The United States declined on Thursday to directly respond to President Mahmoud Ahmadinejad's comment that Iran might be prepared to return to talks with world powers on its nuclear programme.
Instead, senior US officials said Tehran should formally reply to a letter offering talks, but specifying a condition that they focus on specific nuclear issues, sent by the European Union's foreign policy chief Catherine Ashton.
"Our position is that it is as it always has been -- the Iranian regime needs to live up to its obligations to the international community," White House spokesman Jay Carney told reporters aboard Air Force One.
"There is a process by which talks could take place. There is a letter out there from Lady Ashton that the Iranians could respond to."
State Department spokesman Victoria Nuland also said the Ashton letter provided the sole criteria for a resumption of dialogue.
"Just saying you're open for talks doesn't meet the criteria that we have set, which is to be ready for talks and ready to be serious about letting the world know all of the details of your nuclear program and proving your claims that it's for peaceful purposes."
Ahmadinejad said earlier that Iran would not be opposed to returning to the negotiating table.
"They have this excuse that Iran is dodging negotiations while it is not the case," he was quoted as saying by state media.
"A person who has logic and has right on his side, why should (he) refrain from negotiations?" Ahmadinejad asked rhetorically.
Ashton sent Iran's nuclear negotiator Saeed Jalili a letter in October on behalf of permanent UN Security Council members Britain, China, France, Russia and the United States, plus non-permanent member Germany.
It stated that "we can achieve a full settlement only by focusing on the key issue, which are the concerns about the nature of your nuclear programme, as reflected in IAEA reports."
The last talks between the two sides took place in Istanbul a year ago and produced no results.