"Energy prices are rising the entire time which is why the whole issue to do with nuclear energy is back on the agenda not just of this country but many other countries round the world," Blair told MPs.

He said 50 to 60 nuclear power stations were being built around the world this year including one in Europe.

"When we look at our own self-sufficiency in energy we're about 80-90 percent sufficient in oil and gas - over the next 15-20 years that's going to reverse. We'll have to import it," the prime minister said.

"I am not saying only nuclear is the answer - of course it's not, there are renewables, there is energy efficiency, there is everything else - but I still think that that has got to be at least part of the debate and argument if we are to make sure that our energy needs are properly and cleanly met."

Environmentalists oppose the development of new nuclear power stations to replace old ones. They argue that Britain can meet its future energy needs and cut polluting emissions without such a move, especially since no conclusive solution has been found to deal with the problem of radioactive waste.

Britain, which is undertaking a major energy policy review, has about a dozen nuclear power stations, most of them built in the 1960s and 1970s.

Turning to climate change, which featured prominently at a summit of the Group of Eight (G8) world powers last July hosted by Britain, Blair warned that the process of global warming may be happening faster than anticipated.

"My greatest worry is that there is a mismatch between the timing of the international community to get the right agreements in place and the absolute necessity of taking urgent action now," he added.

"But it should be certainly done in the way to fully eliminate concerns of the world community on the non-proliferation issues," Putin said.

"Russia has always been a persistent and reliable partner of Iran," the Russian president remarked. "I am confident that you have no doubts about it," Putin told the Iranian leader.

Putin offered to discuss the proposals made by the six mediators to settle the situation around the Iranian nuclear program. "I would like to learn your view on those proposals that were made," he added.

Putin also brought up Russia's offer to set up a uranium enrichment joint venture, as well as the global initiative to create a network of international nuclear centers. "The access to technologies should be equal, free and non-discriminatory, and the control should be effective," he said.

South Korea is understood to have urged its neighbour not to go ahead with the test, which could take place as soon as the launch pad is completed and the missile injected with solid fuel. Test-launching an intercontinental ballistic missile would cast doubt on the future of six-party talks on ending Pyongyang's nuclear weapons programme.

On Wednesday the US ambassador to Seoul, Alexander Vershbow, warned that Washington would take "appropriate measures" should the launch go ahead. Those could include tightening its squeeze on alleged North Korean money laundering and counterfeiting operations.

Calls for a tougher stance are growing in Japan, which this week passed a law requiring the government to impose economic sanctions against Pyongyang unless it provides reliable information about the fate of eight Japanese abducted by North Korean spies during the cold war.

A Japanese foreign ministry official refused to discuss intelligence details but warned that any launch could have grave consequences for North Korea's already shaky relations with the US and Japan.

"It would be stupid to do that at a time when the US and other parties are involved 120% on Iranian affairs," he said in a reference to pressure on Tehran to give up its alleged nuclear ambitions. "A launch would cause anger and emotion in the US and be regarded as a calculated manoeuvre against the US while it is concentrating all of its efforts on Iran."

"If North Korea fires a missile now while the six-party talks remain off and questions are being raised in the international community about the effectiveness of the talks, there is a possibility it will have a seriously negative impact on the resolution of the North Korean nuclear problem," said the South Korean foreign minister, Ban Ki-moon.

North Korea left the nuclear nonproliferation treaty in 2003 and early last year declared that it had developed nuclear weapons. The multi-party talks, last held in November, have failed to make a breakthrough and no date has been set for the next round.

Christopher Nelson, an analyst at Samuels International in Washington, said in a briefing: "With the implied intelligence confirmation, an interesting element is an emerging sense that if Kim Jong-il goes ahead with his test, for once [the] Dear Leader may have out-smarted himself. That's because it seems genuinely true that both South Korea and China would be displeased."

North Korea provoked widespread anger in 1998 when it launched a medium-range Taepodong-1 ballistic missile over Japan that landed in the Pacific. It has since tested several short-range missiles, including two in March, but hasn't test-launched long-range weapons since 1999.

The Lucas Heights plant was built in 1958 and is used only for research and to produce radioactive material for medical and industrial purposes.

But the incident has proved an embarrassment for Howard's government, which is trying to build support for nuclear power plants in Australia and last week announced a wide-ranging review of the industry.

For the opposition Labor Party, which opposes nuclear power, the incident was a timely boon.

"Accidents like this show that the community is right to be concerned about the safety of nuclear reactors," said the party's deputy leader Jenny Macklin.

"This accident is a stark reminder that things can go wrong with nuclear reactors."

ANSTO said the pipe ruptured inside an area producing medical isotypes. It said small amounts of gases were released routinely and did not pose a threat to the public.

"The releases which occurred last Thursday evening were not outside the normal release pattern, were well within regulatory limits and could not be detected off-site," the organisation said in a statement, adding the incident did not occur in a reactor and had "nothing to do with reactor safety".

ANSTO said that supplies of an isotope used for medical scans would be rationed while it investigates the leak.

Several hospitals across the country would only receive 55 percent of their normal weekly order and would have to prioritise which patients received scans, the organisation added.

Science Minister Julie Bishop accused Labor of "deliberate scaremongering".

"This is just a beat-up by Labor trying to deflect from the fact that we're having an open debate on nuclear power," she said.