But the head of the International Atomic Energy Agency, Mohamed ElBaradei, who met in Vienna last week with Iran's top nuclear negotiator, said the question of Tehran's sensitive atomic research activities was still under discussion.
Mr ElBaradei made his remarks to reporters in Washington after conferring with US Secretary of State Condoleezza Rice on Western efforts to rein in Iran's suspected bid to develop a nuclear bomb.
Iran has publicly insisted on its right to enrich uranium on its soil. Yet
Mr ElBaradei suggested that Tehran's position was more flexible.
"The Iranians, as far as I know, agreed in principle that for a number of years (uranium) enrichment should be part of an international consortium outside of Iran," he said.
Research and development
He said the Iranians told him that once negotiations resumed on their nuclear program, they were ready to apply the "additional protocol" to the Nuclear Non-proliferation Treaty aimed at tightening inspections.
"There is still this issue of Iran doing R and D (research and development) with regards to enrichment and that's an issue still being discussed,” Mr ElBaradei said.
Mr ElBaradei, who sat down in Vienna last week with senior Iranian official Ali Larijani, said he briefed Ms Rice on Tehran's position "which is rather different than the US point of view."
The IAEA chief spoke as senior officials of six world powers met in London to hammer out a new carrot-and-stick approach to persuade Iran to abandon any attempt to make nuclear arms.
The strategy would combine technology, economic and other incentives for Iran with the threat of an arms embargo and other sanctions if the Islamic republic defied a UN injunction to halt enrichment.
Mr ElBaradei has called for more direct US involvement in the discussions with Iran, which so far have been led by US allies Britain, France and Germany, but said it was up to Washington what role it chooses to take.
No negotiations
Earlier the White House insisted that there would be no direct negotiations with Iran unless it suspends its uranium enrichment program altogether.
"Iran has to take that fundamental step when it comes to enriching and reprocessing uranium, they've got to suspend all activities," White House spokesman Tony Snow told reporters.
Without such a step, Mr Snow said, there will be "no change in the administration's posture and the president's posture when it comes to one-on-one negotiations" over Tehran's nuclear program.
"We think that Iran needs to be very serious about suspending all enrichment and reprocessing (of) uranium. They have to agree to do it," the spokesman said.
"They have to do it in a verifiable and credible manner, and a permanent manner," Snow added.
"The first precondition right now -- and we've been working with our allies on this -- is to make sure that Iran does nothing in terms of advancing its ability to build nuclear weapons," he said.