How do you feel about a nuclear weapon that could be launched from the back of a jeep?

The slightly bizarre idea of 'user-friendly' nuclear weapons. On the whole score of proliferation we're always hearing plenty about the dangers posed by the Irans and North Koreas of this world but, as we're about to see, while all that has been going on the US itself has been quietly beavering away on a program aimed at completely upgrading its nuclear arsenal, including the development of tactical weapons - mini-nukes that could be used on the battlefield.

(Click link above to view the interview. Click below to expand for Transcript)

REPORTER: Thom Cookes

AMBASSADOR LINTON BROOKS: I'm going to assume that, for the foreseeable future, that we are going to need to retain nuclear weapons and we're going to need to retain the capability to sustain and, if necessary, modernise them.

REPORTER: Is the US, right now, developing new nuclear weapons?

HANS KRISTENSEN, FEDERATION OF AMERICAN SCIENTISTS: Right now? It's in the process of developing a replacement for its entire stockpile.

REPORTER: How is that affecting the talk in the Administration about arms control?

DARYL KIMBALL, DIRECTOR, ARMS CONTROL ASSOCIATION: Well, you're assuming that there's talk in the Administration about arms control, which there isn't and frankly, this program is not well known outside the US at this stage. It's not even all that well known within Congress.

At the same time that the US is applying extreme pressure to North Korea and Iran to drop their nuclear programs, it's quietly preparing for a new atomic age.There's a push to develop new, more user-friendly weapons, such as nuclear bunker-busters, that could completely change the way wars are fought.

GENERAL EUGENE HABIGER: In my view, that is a mistake, because what you are doing, what we are doing is developing a nuclear weapon that becomes more viable to use, more attractive to use, and nuclear weapons are so horrific that it does not make sense to develop a weapon that is more attractive to use.

Throughout the four decades of the Cold War, the US maintained and developed a massive nuclear arsenal designed for just one purpose - the total annihilation of the former Soviet Union.All the thousands of bombers, ballistic missiles and nuclear submarines were designed to deter the Soviets from even thinking of using their weapons.

DR STRANGELOVE, MOVIE CLIP: Deterrence is the art of producing in the mind of the enemy the fear to attack.

The 1963 film 'Dr Strangelove' parodied the idea of "Mutually Assured Destruction", a guarantee that any nuclear war was unthinkable as it would result in the end of both the US and the Soviet Union.

DR STRANGELOVE: You're talking about mass murder, General, not war.

Mr President, I'm not saying we wouldn't get our hair mussed but I do say no more than 10-20 million people killed, tops, ah, depending on the breaks.

This declassified footage from 1953 shows the only test ever conducted of a atomic cannon.Almost from the beginning of US nuclear research, weapons designers were working on some extraordinary prototypes, weapons they believed could be used in a limited nuclear exchange, short of all-out war.

VOICE-OVER: This film shows the preparation, transport, delivery and emplacement of the SADM in typical parachute missions by swimmers.

The Special Atomic Demolition Munition or SADM, was a nuclear bomb strapped to the chest of a Navy Seal diver.

VOICE-OVER: The time delay between arming and detonation, pre-set during preparation of the munition, allows the swimmers time to make a safe escape.

The SADM was still in the US stockpile up until the late 1980s.

VOICE-OVER: The objective of this operation is to demonstrate the Davy Crockett.

The Davy Crockett was a tiny nuclear weapon that could be fired from the back of a Jeep. This film, from 1962, shows troops testing it out in the Nevada desert.

VOICE-OVER: The round was launched at H-17 seconds to accomplish H-hour impact on the desired ground zero at a range of 2,852m. The round was set for a low height of burst. It detonated perfectly, releasing its lethal radiation.Immediately following the exercise the battalion employed standard unit decontamination procedures to ensure that…

GENERAL HABIGER: We were involved with the recoilless rifle and its accuracy and range and that sort of thing, so that kind of set the stage, in my early, formative years.

General Eugene Habiger helped test the Davy Crockett as a 19-year-old army private. He went on to become the Commander-in-Chief of all US nuclear forces, and, up until the late '90s, it was General Habiger who would have received the call from the President to launch the missiles.

REPORTER: How did you feel about a nuclear weapon that could be launched from the back of a jeep? It's a rather extraordinary proposition.

GENERAL HABIGER: Well, as a 19-year-old young man I really didn't think much about the consequences at that time.

NEWSREADER: Soviet television's lengthy announcement last night of Mr Gorbechev's proposed timetable to remove from the world all nuclear missiles within 15 years..

With the end of the Cold War there was a global push for disarmament. The major nuclear powers had agreed to a ban on any weapons testing at all, and there was a hope that this was the beginning of the end for nuclear weapons.But in the US research labs, the fascination with small, usable nuclear bombs continued, and in the early 1990s it culminated in a weapon nick-named the PLYWOOD, or precision low-yield weapons design.

HANS KRISTENSEN: There were people from the airforce and the labs that came out and sort of talked in, sort of, almost elaborate terms, glorifying terms about this fantastic weapon that you could just use without any real concern about vast collateral damage. For them it was just about destroying targets, it was just a solution. They talked about mini-nukes, micro-nukes - tiny little bombs that you could pop off here and there.

REPORTER: This is the mid '90s we are talking about?

HANS KRISTENSEN: Early '90s, yeah.

Hans Kristensen is a researcher at the Federation of American Scientists, and compiles the definitive annual survey of the world's nuclear weapons. He says Congress was deeply concerned by the development of mini-nukes, like this suitcase bomb.

HANS KRISTENSEN: It showed that we were not, in fact, reducing the role of nuclear weapons, we were just finding new ways of using them, and there was a strong push at the time to significantly reduce the role of nuclear weapons, not just the number of weapons but the intention we had for their use.And so they slammed the door. They put in legislation, I think in '93, that said they banned the labs, the Department of Energy, from doing any work on weapons that had yields below 5 kilotons, even design works, nothing.

Developing new weapons had become politically unacceptable, but in the research labs and the Pentagon, the work on new bombs continued, except now it was virtually in secret.

FILM: This is the story of the B61, the story of a nuclear weapon from concept to stockpile.

The B61 was designed in the 1960s. In the mid '90s it was modified to become the very first nuclear bunker-buster, a bomb designed to destroy deeply buried underground targets. It became one of the most controversial weapons in the US stockpile.

HANS KRISTENSEN: Early on in the conceptual phases, in '92, '93, '94, in those years, it was pretty much in the dark.But it was interesting to note from some of the documents I got out under the Freedom of Information Act, that you could see how the military would play the political situation in Congress, at some point, when they were ready, actually, to go to Congress and say, "Buy this weapon," They said, "No, let's wait a minute, let's wait a few months here, because we're going to get an election a few months down the road and the indications are that the political climate will change, so it will be more conservative and there'll be a bigger chance we can get that."You can actually see this. They write this in the documents. "When is Congress going to be politically favourable to us?"

In November 1994 the Republicans gained control of Congress for the first time in 40 years, and the B61 bunker-buster project was swiftly approved.By 2002, with George Bush in the White House gunning for North Korea and Iran, the climate had changed entirely.

GEORGE BUSH, US PRESIDENT: States like these, and their terrorist allies, constitute an axis of evil, arming to threaten the peace of the world.The United States of America will not permit the world's most dangerous regimes to threaten us with the world's most destructive weapons.

After pressure from his Administration, the ban on the development of mini-nukes was quietly lifted in 2003. Ambassador Linton Brooks, a former nuclear submarine commander, is the head of the National Nuclear Security Agency and is responsible for managing the US weapons arsenal.After the mini-nuke research ban was lifted he sent an extraordinary memo to the directors of the three nuclear research labs. Claiming that the ban had caused a "chilling effect on nuclear weapons research and development", he thanked the labs for their support in overturning it, saying that they "should not fail to take advantage of this opportunity."

DARYL KIMBALL: Essentially what Ambassador Linton Brooks told the three lab directors was "The ban on low-yield nuclear weapons research has been lifted. Your hands are now untied, move ahead with all speed, and go get 'em boys."That was the message, and that was a bit shocking to the congressional committees who had just allowed this ban to be lifted.

The congressional committee was furious with Brooks, accusing him of lying to them. They sent back a blistering memo saying that the only message Brooks had conveyed to the weapons labs was "that of unbridled enthusiasm for new weapons designs, and for seeking new military missions for nuclear weapons".What Brooks asked the labs to work on was a new, improved version of the nuclear bunker-buster, now known as the Robust Nuclear Earth Penetrator. This cold war warrior is one of the few Administration figures prepared to spell out the new nuclear agenda.

LINTON BROOKS: It is the belief of some of us that the large arsenal we have aimed at destroying an urban industrial infrastructure is not an appropriate deterrent for some potential adversaries, and therefore that one might want to look at other capabilities, and that has led to the call for some kind of earth penetrating weapon.

REPORTER: This is about the Pentagon being able to threaten or deter, if you like, North Korea or Iran or other countries from having very heavily defended and buried labs for weapons of mass destruction?

DARYL KIMBALL: Yes, they want to hold at risk these facilities. They want to have a weapon in the arsenal that could theoretically be used to knock out a facility 100ft, 200ft underground.

Critics say that conventional weapons could do the same job.

GENERAL EUGENE HABIGER: It's a whole new dimension, now, with precision guided munitions where you can put a warhead through a door in an underground bunker and especially with some of the technologies we've got available to us today.

HANS KRISTENSEN: If you have to take out a facility, an underground facility, why would you nuke it? Why not seal the entrances? Why not make it unusable?

The Robust Nuclear Earth Penetrator was initially sold as a clean, surgical weapon. It was claimed that since most of the blast would be directed underground there would be a reduced risk of radioactive fallout. But the US Government's own tests showed otherwise.

FILM, VOICE OVER: The 100 kiloton explosion excavated more than 6 million cubic yards of earth in a matter of seconds.The result was a crater more than 1,200 feet in diameter, the length of four football fields and 325 feet deep - the height of a 32-storey building.

This 1962 film shows an underground nuclear explosion only a third of the size that would be produced by the new bunker-buster.Far from being contained, half of the radioactive material was distributed as fallout over a large area, despite the charge being buried almost 200m underground.During testing, it's been discovered that bunker busters are unlikely to penetrate more than about 10m.

GENERAL EUGENE HABIGER: If you use a nuclear weapon, a earth penetrator, you are still going to get ejected, coming out of the radioactive material, coming out of the crater, which is going to go into the atmosphere and kill several tens of thousands or tens of millions of people, depending on where it is used.

The Nuclear Earth Penetrator project has so far been too controversial for even a Republican-controlled Congress to approve, and for the last two years, it has knocked back funding requests by the Bush Administration.

LINTON BROOKS:: The truth of the matter is that it's the same thing we did 10 years ago with the B61-11, only better, and I suspect that the number of Americans who know what the B61-11 is would fit pretty comfortably into this room and the number who care would fit into a somewhat smaller room.

The nuclear bunker-buster is stalled for now, but its still alive in the minds of the weapons designers and their patrons. Behind the scenes determined lobbying goes on.

DARYL KIMBALL: The civilians in the Defence Dept, within Donald Rumsfeld's office, the office the Secretary of Defence, want this.

GENERAL EUGENE HABIGER: Most of the push is coming from the Department of Energy.

REPORTER: And can you speculate as to why that would be?

GENERAL EUGENE HABIGER: Well, they have a vested interest, this is their they have concerns about the security of the United States, I understand that, but this is their product, and they're trying to sell their product.

But the US Congress has already approved a far more ambitious program. In January this year, Congress agreed to fund the Reliable Replacement Warhead Project, a plan to completely replace the existing Cold War nuclear stockpile. This new generation of weapons is supposed to be cheaper to maintain, safer, and more reliable.

HANS KRISTENSEN: That concept is not one warhead, the concept is a replacement of potentially all the warhead types in the stockpile.

REPORTER: So, yes, they are basically redesigning their entire nuclear arsenal?

HANS KRISTENSEN: They're in the process of essentially gearing up to redoing the nuclear era. The existing ones we've had are weapons that have served us back from the dawn of the nuclear era, so to speak - yes, they've been modernised - but what they're now doing is saying, "That era won't serve us well in the future, we have to do a new one", so they're designing a new nuclear era, if you will.

Defence and the Department of Energy argue that their existing weapons are too expensive to maintain and they'll eventually deteriorate.

HANS KRISTENSEN: I think these weapons we have could serve the nation well for many decades. It's not as if they don't work, or we think they may not work in just a few years or even a decade. I think this has a lot to do with other things and, mind you, these programs will always be sold, with the political message that serves us at the time.

LINTON BROOKS: Some responsible critics of our policies have suggested that US R&D and weapons programs hamper our ability to advance global non-proliferation. I disagree with that.The major non-proliferation objective for the US is to keep rogue states and terrorist groups from acquiring weapons of mass destruction. Our efforts to sustain and modernise US nuclear forces don't increase terrorist incentives to obtain those weapons - those incentives are high and really unrelated to what we do in this area. They don't have much impact on rogue states, whose proliferation activities march forward independently of the US nuclear program.

But not everyone agrees with Linton Brooks' assessment.

HANS BLIX: We have many other perspectives from many other states, parties to the NPT, which point to the fact that they feel cheated.

Hans Blix, the former UN weapons inspector, is in Washington to address an Arms Control Association meeting. Linton Brooks is in the audience.

HANS BLIX: The US points to Iraq and Libya, North Korea and Iran etc, on the other side is saying you are modernising, you are talking about bunker-busters, and Chirac the other day was talking about the possible use of French nuclear weapons in some context.It's not surprising that some people feel ostracised, that they are saying, "If you don't pay any attention to us, maybe we should pursue the bomb."

REPORTER: Do you think the United States's ability to walk into something like the Non-Proliferation Treaty is undercut in any way by the fact that the United States is simultaneously modernising and overhauling its nuclear stockpile? Do you think it is sending out the right message by doing that?

GENERAL EUGENE HABIGER: No, it's not sending out the right message. If you look at the Non-Proliferation review meeting in New York last year, our delegation was dismal at best. Our participation, as I understand it, was not very appealing or attractive.We are passing the wrong signal on several fronts, in my view, about non-proliferation.

But perhaps the greatest great fear of arms control advocates is a resumption of nuclear testing by the US to see if their new weapons will actually work.

LINTON BROOKS: What we have learned, rightly or wrongly, is that it is really difficult to know what you want to do in the future and that has led to a great reluctance to take a formal obligation not to test.So I think the chances of this Administration signing the comprehensive test ban treaty are pretty close to zero.

REPORTER: What would it mean if the US resumed testing? What effect would that have on the US and around the world?

DARYL KIMBALL: It would be absolutely devastating. The US is already testing the patience of the rest of the world by refusing to ratify the treaty. So I think the renewal of testing would be a blow to the NPT. It would also trigger the renewal of testing by other states. I think it would be very hard for the Russian Government to resist pressure from within to resume testing.If the Russians resume testing I think it would also open the way for the Chinese to resume testing. The Chinese tests would lead the Indians to resume testing. The Indians would like to test. If India did, Pakistan would. So we'd have a chain reaction of nuclear testing.