The United States and the European Union said that Iran's recent letter to EU foreign policy chief Catherine Ashton proposing to resume talks showed "a potential possibility that Iran may be ready to start talks."
“I am cautious and I am optimistic at the same time,” Ashton said on Friday after meeting with US Secretary of State Hillary Clinton in Washington.
“We’ll continue to discuss and make sure that what we’re looking at is substantive,” she said.
“It also demonstrates the importance of the twin-track approach, that the pressure that we have put on together, the sanctions that have been put there because that’s the responsibility of the international community, I believe, they’re having an effect. But we, of course, want to resolve this through talks”.
"We think this is an important step and we welcome the letter," Clinton said, stressing that the major powers were still reviewing their formal response to Tehran's offer.
Ashton handles contact with Iran on behalf of the "P5+1" group which comprises the United States, Britain, France, Russia, China and Germany.
Iran's letter to Ashton proposed resuming the stalled talks and said Tehran would have "new initiatives" to bring to the table.
But the brief letter, which responded to a letter Ashton sent to her Iranian counterpart in October, offered no specific proposals, leaving a question mark over Tehran's willingness to enter substantive negotiations on its nuclear program.
Clinton, however, said the Iranian letter "appeared to acknowledge and accept" the western countries' longstanding condition that any talks begin with a discussion of its nuclear program.
"We must be assured that, if we make a decision to go forward, we see a sustained effort by Iran to come to the table, to work until we have reached an outcome that has Iran coming back into compliance with their international obligations," Clinton said.
French Foreign Minister Alain Juppe said on Thursday that a February 20-21 visit to Iran by the International Atomic Energy Agency's chief inspector would help determine whether Tehran was serious about tackling international concerns.