The Prime Minister last night said he would set out within the next few days specific recommendations for a future deal on reducing Britain's nuclear arsenal that could be reached in 2010.
The Prime Minister last night said he would set out within the next few days specific recommendations for a future deal on reducing Britain's nuclear arsenal that could be reached in 2010.
The framework is expected to envisage all nuclear-armed powers reducing their arsenals and offering help to non-nuclear states to develop a civil atomic energy capability in return for assurances that they would not seek to get the bomb.
It came as the Prime Minister indicated Britain would be prepared to negotiate a reduction in its Trident nuclear arsenal as part of multilateral talks in Washington planned for next year.
Proposals to be tabled by Britain as part of a new nuclear deal could see the onus put on states suspected of seeking to acquire nukes, such as Iran and North Korea, to prove that they were not - rather than the rest of the world having to show that they were.
Mr Brown insisted a "more tough regime" was needed given that more states like Iran, a signatory to the NPT, wanted to acquire nuclear weapons in the next decade.
The PM stressed there was no question of the UK offering unilaterally to abandon its 160-warhead Trident arsenal or scrap plans to replace the fleet of four submarines that act as its platform.
He told reporters at the L'Aquila summit: "Iran is attempting to build a nuclear weapon. North Korea is attempting to build a nuclear weapon. We have got to show we can deal with this by collective action.
"Unilateral action by the United Kingdom would not be seen as the best way forward. What we need is collective action by the nuclear weapons powers to say that we are prepared to reduce our nuclear weapons, but we need assurances also that other countries will not proliferate them.
"And we need new kinds of assurances to prevent a situation such as we have got in Iran emerging in exactly the same way again," he added.
Elsewhere, US President Barack Obama confirmed that, as expected, the G5 of developing nations - China, India, Brazil, South Africa and Mexico - had agreed to the plan to limit global warming to no more than 2C, but did not sign up to cutting their emissions by 50% by 2050.
On Wednesday, the G8 agreed not only to the 2C goal but also to cutting their emissions by 80% by 2050.
At a news conference after the forum, the US President said: "I did not expect to solve this problem in one summit but we have made some huge strides forward."
He said getting the G5 to agree with the 2C target was a "further and unprecedented commitment" but that tough negotiations lay ahead before the crunch summit in Copenhagen in December.
Mr Obama added: "I'm the first one to acknowledge progress on this will not be easy."
On trade, the G8 leaders said they wanted to finally seal the long-delayed world trade deal next year and head off trade wars that could hit world economies as they struggle to emerge from recession.
Completing the so-called Doha round of trade talks has risen up the agenda due to fears that the economic crisis will lead to an upsurge in protectionist policies like the ones that helped cause the Great Depression of the 1930s.
"We reaffirm our commitment to maintain and promote open markets and reject all protectionist measures in trade and investment," said a draft of the joint statement signed by 17 nations, including the G8 and G5. Today, the focus will be on development aid when African nations and international organisations join the talks.
Among those attending will be Libyan leader Muammar Gaddafi, who Mr Obama met before yesterday's summit dinner.
It is expected that the G8 leaders will back a move to create a $15bn food security programme to enable poorer nations to feed themselves rather than having to rely on handouts from richer nations.
