"We are going to continue as long as there is no legally binding internationally recognized instrument for assurance of supply," said Ali Ashgar Soltanieh, the chief Iranian delegate to the International Atomic Energy Agency.
However, he declined to clarify whether that meant that Iran would halt its enrichment program in return for such international guarantees, suggesting it might have to continue at a diminished level in case the outside supply stops.
Iran has steadfastly rejected international pressure to give up enrichment, a potential source of both nuclear fuel and fissile warhead material.
The United States says the enrichment program is designed to give Iran a nuclear bomb. David Kay, who led the U.S. weapon hunt in post-invasion Iraq, said Iran was. Iran insists it is for peaceful nuclear power generation.
Soltanieh said Iran is forced to develop its own enrichment facilities to ensure security of supply for its power plants because it fears international suppliers would face pressure from the United States or others to cut deliveries.
That might change if all 145 members of the U.N.'s atomic energy agency concluded a legally binding agreement to guarantee a constant supply of fuel, Soltanieh told reporters after addressing a think-tank conference.
"Then Iran would be able to reconsider the position that we have now," he said.
Iranian Foreign Minister Manouchehr Mottaki, speaking at the Asia Society in New York, also held open the door to negotiations.
Despite differences, Mottaki said enough "common ground" exists to justify more talks over Iran's nuclear program, and "if sufficient political will exists" then an accord can be reached.
At the same time, he questioned the good faith the U.S. and its partners.
"Unfortunately, at the moment in the world today ... we don't see that much fair play out there," Mottaki complained. "Mostly what we see is a selective approach and double standards."
Iranian officials have for years refused to consider calling a halt to the program despite U.N. sanctions.
Getting all members of the Vienna-based nuclear agency to agree on legally binding guarantees would be very difficult, and Soltanieh suggested that Iran may want to keep some enrichment activities even if such an agreement were found.
"We have to have a contingency (safeguard) in case of interruption," he said. "This is not an overnight situation that there is a paper today, and tomorrow then they say Iran will stop. No, it's not possible. There is no way."
Previous efforts to persuade Iran to stop its enrichment program by offering outside fuel supplies, notably from Russia, have failed.
Nevertheless the suggestion that an international supply agreement might end the nuclear stand off was welcomed by Hans Blix, the former head of the nuclear agency and chief U.N. weapons inspector in Iraq. He said it could be the basis for international negotiations.
"This is the direction in which one should look for the future," Blix told the conference on Iran's nuclear program organized by the European Policy Center.