A Kuwaiti offer raised pledged funding for an international nuclear fuel bank over $150 million on Thursday, clearing the way for an action plan to be drawn up by the chief U.N. nuclear monitor, diplomats said.

The International Atomic Energy Agency and industrialized nations see multilateral uranium-enrichment centres as the key to slaking rising demand for nuclear energy without developing nations building proliferation-prone plants on their own soil.

Developing states have reservations, fearing such fuel banks, which would provide enriched uranium from stocks provided by industrialized nations, would curb their sovereign right to homegrown nuclear technology for producing electricity.

Supporters say the idea, decades-old, has taken on urgency given Iran's pursuit of an enrichment industry while curbing the IAEA access needed to verify the programme cannot be covertly diverted to bomb-making. Iran denies any such intent.

More impetus has come from North Korea's nuclear test blast.

Part of an IAEA board of governors' meeting this week was devoted to reviewing progress towards realizing a fuel bank. On Thursday, Kuwait pledged $10 million to the undertaking, diplomats in the closed-door gathering told Reuters.

Kuwait's move fulfilled a target of $100 million in matching contributions stipulated by the Nuclear Threat Initiative think-tank, which launched pledges in 2006 with $50 million offered by U.S. billionaire Warren Buffett.

Then came pledges of $50 million by the U.S. government, 25 million euros ($31.2 million) by the European Union, $10 million by the United Arab Emirates and $5 million by Norway.

IAEA Director-General Mohamed ElBaradei will now draw up a detailed fuel bank plan for consideration at the June meeting of the agency's 35-nation governing body, diplomats said.

"This is clearly not going to happen overnight," he told the gathering in an address earlier this week.

BIG STAKES

But he said bold measures, including assurances of nuclear fuel supply and multinational supervision of sensitive parts of the nuclear fuel cycle, are vital if benefits of nuclear power were to be spread while curbing nuclear weapons proliferation.

A fuel bank would be overseen by the IAEA and ElBaradei said it should ideally have three principles:

* it must be non-political, non-discriminatory and available to all states that comply with nuclear safeguards agreements

* supply of enriched uranium must be based on non-political criteria established in advance and applied consistently

* no nation would be required to cede its right under the Non-Proliferation Treaty to develop its own fuel industry

"The next step would be to agree that all new enrichment and reprocessing centres should be placed under multilateral control, to be followed by agreement to convert all existing facilities from national to multilateral control," he said.

But many developing nations feel the idea could undo their NPT right to indigenous enrichment and keep the lucrative technology in the hands of a small industrialized nuclear club.

Developing countries on the IAEA board made clear their continued concerns in debate this week, diplomats said.

Most notably, Iran, which is under U.N. sanctions for refusing to suspend enrichment, has been dismissive of such proposals if they meant renouncing its own fuel production.

Still, the idea exerts appeal since many developing nations want nuclear energy as an alternative to oil and gas, which are high-polluting, finite in supply and prone to wide price swings.

ElBaradei believes fuel banks would protect recipient states from politically motivated disruptions of supply.

A Russian proposal for a minimum 120-tonne reserve of enriched uranium in Siberia was floated at the IAEA meeting. ElBaradei said Moscow's initiative "provides assured export licenses and covers all long-term costs".