The US and the UN's nuclear watchdog have agreed to work on new rules to curb nuclear proliferation, the UN body's chief Mohamed ElBaradei says.
IAEA chief ElBaradei reported progress on Iran
Mr ElBaradei, head of the International Atomic Energy Agency, was speaking after talks in Washington with President George W Bush.
He said he had told Mr Bush that the "jury was still out" on whether Iran had the means to build a nuclear bomb.
But Mr ElBaradei said Iran was now co-operating fully with the IAEA.
They discussed tightening curbs on proliferation after revelations that a top Pakistani scientist, Dr Abdul
Qadeer Khan, had sold weapons technology on the nuclear black market.
The meeting between President Bush, his security adviser Condoleezza Rice and Mr ElBaradei brought agreement that curbs on the purchase and maintenance of nuclear material needed to be strengthened.
"This is a whole different ball game and we need to change many of the rules," Mr ElBaradei said after the meeting.
In particular, he said, agreement with the US had been reached on the need to "revisit the whole export control regime... as a result of AQ Khan associates and the lesson we have learnt from that".
Dr Khan, hailed by many Pakistanis as the father of the "Islamic bomb", confessed in January to operating a network that hawked nuclear secrets to states such as Iran, Libya and North Korea.
'Talk to Iran'
Questions over Iran's nuclear potential dominated the Bush-ElBaradei meeting.
Mr ElBaradei said he had urged the US administration to pursue dialogue with Iran to defuse tensions.
The Bush administration has accused Iran of enriching uranium for bomb purposes - a charge Iran denies, maintaining it needs the uranium to generate power for civilian needs.
Anti-proliferation measures discussed in the meeting included a moratorium on states attempting to enrich uranium.
Mr ElBaradei supports the idea of a cut-off point, beyond which nations will be offered low-grade uranium - of the type useful only in power stations - in exchange for renouncing the quest for weapons-grade enriched uranium.
A similar programme is already being tried out with Libya, which opened its doors to UN inspectors late last year.
"My suggestion to the president is that we need a good plan to clean up all this nuclear weapons-usable material that is all over the place," Mr ElBaradei said.