It came after Iran's top nuclear official said that Tehran could consider continuing a suspension of uranium enrichment, as demanded by Britain, France and Germany.

The three countries presented Iran with a deal last week under which Tehran would receive valuable nuclear technology if it promised it was not trying to build atomic weapons, including indefinitely suspending all uranium enrichment activities, a key stage in the nuclear fuel cycle.

"The European proposal for an unlimited suspension of uranium enrichment can be implemented, provided it does not contradict the Islamic republic's criteria," Iran's chief nuclear negotiator Hassan Rowhani said, according to state television.

"The meeting will take place Wednesday," a diplomat said in Vienna.

The UN nuclear watchdog said that while it was not formally involved in the talks, it was following them with interest.

A spokeswoman for the International Atomic Energy Agency said its director Mohamed ElBaradei "was briefed by both parties directly after the meeting last week.

"He believes that this is moving in the right direction, and we now welcome this constructive dialogue."