A senior UN nuclear agency team will visit Tehran on January 28, with Iran saying it is ready to discuss allegations that it was involved in secret nuclear weapons work, diplomats have said.
Diplomats have previously said that International Atomic Energy Agency (IAEA) officials were discussing such a trip with their Iranian counterparts.
But before the diplomats' comments, no date - or indication that Iran was ready to talk about the allegations - had been mentioned.
Any follow-through on the part of Iran on its reported pledge to discuss nuclear arms suspicions would be significant.
For more than three years, Tehran has blocked IAEA attempts to follow up on US and other intelligence alleging covert Iranian work on nuclear arms, dismissing the charges as baseless and insisting all its nuclear activities were peaceful and under IAEA review.
Faced with Iranian stonewalling, the IAEA summarised its body of information in November, in a 13-page document drawing on 1,000 pages of intelligence. It stated then for the first time that some of the alleged experiments can have no other purpose than developing nuclear weapons.
Iran continues to deny the charges and no change in its position is expected during the Tehran talks with IAEA officials. But even a decision to enter a discussion over the allegations would be a major departure from outright refusal to talk about them - and create hopes of future progress in the investigation.
Two diplomats told The Associated Press that Iranian officials had suggested they were ready to talk about the issue during recent meetings with officials of the Vienna-based IAEA.
Ali Asghar Soltanieh, Iran's chief IAEA delegate, declined to be drawn on what would be discussed in Tehran, indicating in comment that it was too early to go public with details.
Beyond the dispute over Iran's nuclear intentions, US-Iranian relations have been further burdened by an Iranian announcement that a joint US-Iranian national will be executed after being found guilty of spying - a charge both he and Washington denies. Iran, in turn, sees possible US complicity in a series of assassinations of its nuclear experts - the latest on Wednesday, when scientist Mostafa Ahmadi Roshan was killed by a bomb attached to his car by a passing cyclist.