The Bush administration is considering a change in international rules to prevent countries like Iran from legally acquiring components for a nuclear weapons program, senior US officials say.
The goal is to strengthen the nuclear non-proliferation Treaty, cornerstone of efforts to stem the spread of atomic arms, by closing what is now viewed as a major loophole.
The initiative is similar to a deal that France, Germany and Britain recently offered Iran and to proposals advocated by some of Washington's most respected security experts.
It is still in early discussions but may be formally advanced at the June 8 US-hosted summit of the Group of Eight major industrialised countries, US officials told Reuters.
Under a bargain struck when the NPT took effect 33 years ago, most countries pledged never to acquire nuclear weapons.
In return, they were promised that the five declared nuclear weapons states - the United States, Russia, France, Britain and China - would help them acquire nuclear technology for peaceful uses, namely nuclear power plants.
However, US officials and experts say it is clear that some NPT signatories - like Iran, Libya and North Korea - exploited the pact to acquire technology that brings them close to being able to produce nuclear weapons.
In general, the proposal now under discussion in Washington would guarantee and even enhance the ability of non-nuclear weapons states to obtain nuclear power for electricity.
But they would be denied the right to manufacture, store or reprocess nuclear fuel - a key component of nuclear bombs.
"A lot of people have been talking about that and we're considering it - cutting off enrichment and reprocessing technology to close the loophole while guaranteeing them (non-nuclear states) access to fuel," one US official said.
"Guaranteeing these states access to (nuclear) fuel has its own risks, but it's better than allowing them to have enrichment and reprocessing capabilities ... We may well do that in the G8 context," he said.
The official added: "It's obvious that there is a problem with the NPT when a country can stay in compliance with it and still get very close to a nuclear weapons capability."
Experts say acquiring weapons-grade material is the biggest hurdle countries face in seeking to make atomic bombs.
President George W. Bush put a new spotlight on Iran's ambitions in 2002 when he accused the Islamic republic of being part of an "axis of evil" - with North Korea and Iraq - bent on acquiring atomic arms.
Later, the UN nuclear watchdog, the International Atomic Energy Agency, found traces of bomb-grade highly enriched uranium at two sites in the country.
Iran insists its nuclear program is purely peaceful. Libya, on the other hand, recently agreed to dismantle its nuclear program while North Korea, having withdrawn from the NPT, claims its nuclear activities are proceeding.
Writing in the New York Times last month, former national security adviser retired Lieutenant General Brent Scowcroft, former Defense Secretary William Perry and two other former officials - Arnold Kanter and Ashton Carter - outlined their proposal.
Nuclear countries should withhold nuclear power technology from states that do not forsake atomic weapons but should offer a reliable source of nuclear fuel to, and retrieval of spent fuel from, states that do forsake atomic weapons, they said.
They urged Washington to propose that Russian plans to help Iran build a network of civilian nuclear power reactors be permitted to proceed - as long as Tehran agrees to a verifiable ban on enrichment and reprocessing and lets a Russian-led consortium handle its nuclear fuel needs.