Iran's Supreme Leader, Ayatollah Ali Khamenei, has said his country is ready to share its nuclear technology with other nations.
Ayatollah Khamenei's offer comes ahead of a UN deadline
Ayatollah Khamenei made the offer during a meeting with visiting Sudanese President Omar al-Bashir.
US Secretary of State Condoleezza Rice condemned the comments.
Earlier, Iran's top nuclear negotiator threatened to suspend co-operation with the UN's nuclear watchdog if Teheran faced sanctions over its nuclear work.
The UN Security Council has set a deadline of 28 April for Iran to freeze its programme of uranium enrichment, which has been the focus of concerns that Iran could acquire nuclear weapons.
The US is trying to rally support from the Security Council for tougher action against Iran, including sanctions - a move currently being resisted by Russia and China.
In his meeting with Mr Bashir, Ayatollah Khamenei said Iranian scientists' nuclear capability was "one example of the numerous scientific movements in the country".
"The Islamic Republic is ready to transfer this experience and the technology and knowledge of its scientists," the leader was quoted as saying.
In return, the Sudanese president praised Iran's enrichment of uranium as a great victory for the Islamic world.
Mr Bashir said last month his country was considering creating a civilian nuclear programme.
Ms Rice said she feared an "escape... of knowledge and expertise on these dangerous technologies".
Last year, Iran's President Mahmoud Ahmedinejad spoke of sharing nuclear technology with other countries.
But the BBC's Frances Harrison in Tehran says that this time the offer comes from the very top, and seems to imply the technology could be shared with Sudan.
As well as threatening to end Iranian co-operation with the UN, negotiator Ali Larijani said Iran would "hide" its nuclear programme if it was attacked.
"They [Western countries] have to understand they cannot resolve this issue through force," Mr Larijani told a conference on Iran's controversial nuclear energy programme in Tehran.
Larijani has threatened to cold-shoulder the IAEA
Responding while on an official visit to Greece, Ms Rice said Iran's threats were "emblematic of the kind of Iranian behaviour seen over the past couple of years".
Ms Rice said the Security Council must now issue something more concrete than last month's "presidential statement", which gave Iran 30 days to comply with International Atomic Energy Agency (IAEA) directives.
Iran insists its nuclear programme is for civilian energy purposes only. The US and several other nations say they do not believe this.