VIENNA, Austria - New doubts are arising about the accuracy of U.S. intelligence on the nuclear programs in North Korea and Iran, only a few years after faulty warnings about weapons of mass destruction helped President Bush justify the invasion of Iraq.

North Korea agreed earlier this month to dismantle its plutonium-producing nuclear facilities in exchange for economic aid and security assurances from the United States and four other world or regional powers. The pact successfully put aside for now the possibility of military action.

But the Western standoff with Iran remains tense. The Bush administration says it won't rule out an attack if Tehran refuses to end its nuclear enrichment program.

However, in both cases, once-strident U.S. pronouncements about the programs - which raised the tension level with Pyongyang and Tehran along with Saddam Hussein's Iraq - are apparently being replaced by less alarming assessments.

Just weeks after the Feb. 13 six-nation pact with North Korea, new U.S. statements suggest that Washington might have overstated a purported secret North Korean second-track nuclear program. The result was that it derailed what could have been a peaceful resolution to the North Korean issue more than four years ago.

The U.S. alleged then that North Korea had a large-scale gas centrifuge plant for uranium enrichment - the same program Iran now is developing. The Bush administration used that information to scrap a plan developed under the Clinton administration to supply energy to the North in exchange for its pledge to mothball its plutonium program.

Tensions rose and Pyongyang withdrew from the Nuclear Nonproliferation Treaty in January 2003, sparking the process that led to its test of an atomic weapon late last year.

Now, however, Bush administration officials are toning down assertions that such a program had been developed. Intelligence official Joseph DeTrani, in testimony to the Senate Armed Services Committee, said Tuesday belief that such a program exists was now "at the mid-confidence level."

The "mid-confidence" terminology means that analysts have differing views or credible information exists but has not been fully corroborated. That's a notable departure from the previous U.S. view of "high confidence" that the North was working on such activities.

Assistant Secretary of State Christopher Hill said Wednesday that the U.S. knows that North Korea has bought equipment that could be used only for uranium enrichment. But he expressed uncertainty about the program's current state.

"How far they've gotten, whether they've actually been able to produce highly enriched uranium at this time - I mean these are issues that intelligence analysts grapple with," Hill told a hearing of the House Foreign Affairs Committee. "But what we know is they have made the purchases, and we need to have complete clarity on this program."

A U.S. government official, speaking on condition of anonymity because of the subject's sensitivity, said there was no change in the intelligence assessment. Degrees of certainty were always reflected in the CIA's judgment, the official said.

The U.S. intelligence community found with "high confidence" in 2002 that North Korea obtained components that could be used to enrich uranium. However, there has always been less confidence in the analysis of what precisely North Korea planned to do with the components, the official said.

It was a worst-case scenario when a CIA paper in 2002 stated that the plant "could produce enough weapons-grade uranium for two or more nuclear weapons per year when fully operational - which could be as soon as mid-decade."

The next line of the paper highlighted the uncertainty, reminding readers that North Korea's nuclear program was "a difficult intelligence collection target."

Bush said on Nov. 7 of that year that Pyongyang was "enriching uranium, with the desire of developing a weapon."

Chief U.N nuclear inspector Mohamed ElBaradei has been invited to Pyongyang in mid-March for a visit expected to result in the return of his inspectors after a four-year hiatus.

The U.S. intelligence record on Iran's nuclear activities also is being questioned.

Several senior diplomats familiar with work of the Vienna-based
International Atomic Energy Agency, which ElBaradei heads, told The Associated Press that while U.S. intelligence helped reveal Iran's secret nuclear program in 2002, none of the information provided the U.N. nuclear watchdog by American spy agencies since then had led to meaningful leads. Still unproven is whether Tehran is using the cover of a nuclear power plant program to try to make atomic weapons.

One of the diplomats - who, like others demanded anonymity because he was discussing confidential information - said that in the case of Iran, lack of good intelligence was due to "no presence on the ground." Intelligence is increasingly scarce because "the Iranians have tightened up on their operations" since the 2002 revelations about their secret uranium enrichment program, he added.

Broad assessments often hinge on detailed information about equipment, which can be difficult to prove.

For North Korea, a key U.S. assertion that Pyongyang was trying to create an industrial-scale uranium enrichment program parallel to its plutonium operations was based on evidence that the North Koreans had purchased or were trying to buy thousands of highly machined aluminum tubes, he said. The CIA cited Iraqi purchases of such tubes to support its assertion about a purported nuclear weapons program under Saddam.

A CIA fact sheet made public four years ago claimed "clear evidence indicating that the North has begun constructing a centrifuge facility," and estimated it could produce material for at least two or more nuclear weapons a year by 2005.

Former U.N. nuclear inspector David Albright, who recently visited Pyongyang and held talks on the North's nuclear program, does not question U.S. assertions that the North bought a few dozen centrifuges from the same Pakistani black market network that supplied Iran's program.

"However, a large centrifuge plant likely does not exist; perhaps it never did," says Albright in a report of his Washington-based Institute for Science and International Security that tracks the North Korean and Iranian nuclear programs.

The diplomat agreed, noting it made no sense for the energy-starved North - which is to get the equivalent of up to 1 million tons of heavy fuel oil under the nuclear disarmament deal - to run such a program consuming record amounts of power at a time it was making good progress on its plutonium-based arms program.