The United States held the highest level direct talks with Iran in three decades today to try to put to rest Western suspicions Tehran is planning to build nuclear weapons.
The "significant" bilateral conversation took place during talks between Iran and six world powers near Geneva, an official at the talks said.
Secretary of State Hillary Clinton called the talks "productive" but said she wanted to see Iran take concrete actions.
"There were a number of issues raised, put on the table, and now we have to wait and see how quickly and whether Iran responds," Mrs Clinton told reporters in Washington. "I think it was a productive day but the proof of that has not yet come to fruition so we will wait and continue to press our point of view and see what Iran decides to do.
"I will count it as a positive sign when it moves from gestures and engagement to actions and results," she added. "We want to see concrete actions and positive results and I think today's meeting opened the door but let's see what happens."
The negotiations outside Geneva, also attended by Britain, France, Germany, Russia and China, took place against a backdrop of renewed international concern prompted by Iran's revelation it has a second uranium enrichment facility.
Washington had said it would not threaten further sanctions against Tehran at the one-day meeting but had prepared them in case the discussions made no progress.
Tehran says its nuclear program is designed purely for generating electricity and had ruled out discussing it, saying the talks should focus on issues like Afghanistan instead. But a Western diplomat close to the meeting said Iran's nuclear negotiator had touched on it in his opening statement.
The diplomat said the issue of the second enrichment facility at Qom had been raised. The West wants Iran to allow immediate UN inspections at the plant, which Tehran revealed last week, and give access to documents and employees. The diplomat said it was not yet clear if the Iranians would compromise on the wider issue of suspending uranium enrichment, as demanded by five UN Security Council resolutions.
Iranian state television said later the two sides would meet again this month. There was no immediate confirmation.
An Iranian official who declined to be named said Iran wanted the talks to succeed. "We want logic to dominate the atmosphere of the talks," the official said.
In Washington, senior Obama administration officials said the United States would not threaten Iran with fresh sanctions.
But one official said the United States has been preparing "a range of areas" in which to pursue sanctions if Tehran ignores Western entreaties about its nuclear program.
Washington severed relations with Tehran in 1980 during a hostage crisis in the wake of Iran's Islamic Revolution.
The administration of former president George W. Bush reluctantly began to take part in multilateral talks with Iran toward the end of his presidency. President Barack Obama has said he wants to improve US-Iranian ties but Tehran has reacted coolly to his overtures.
Mr Ahmadinejad said in New York last week his delegation would ask at the Geneva meeting that Iran be allowed to buy enriched uranium for medical purposes from the United States or any other country prepared to sell it.
A US official said Washington would make clear that it was not prepared to sell Iran any uranium.
The Western powers also want to gauge Russian and Chinese reaction to last week's announcement that Tehran had been concealing the uranium enrichment plant at Qom. Western diplomats said Moscow and Beijing seemed to share their concern.
Nato secretary-general Anders Fogh Rasmussen said in London he hoped Iran realised it had to abandon its nuclear plans.
"Recent events including the fact that Iran had not declared the existence of a nuclear site testifies to the importance of this issue and stresses the need for an increased international, political and diplomatic pressure on Iran," he told reporters.
Reuters