The UN nuclear watchdog, the International Atomic Energy Agency, has begun a meeting in Vienna to discuss a report on Iran's nuclear activity.
Speaking before the meeting, the head of the IAEA, Mohamed ElBaradei, said he was hopeful that a deal over Iran's atomic programme could be reached in the next week or so.
He said international peace and security were at stake in efforts to resolve the crisis.
Western powers believe Iran wants to develop nuclear weapons, but Tehran says its plans are for civilian energy.
Months of failed negotiations have led to today's meeting.
Earlier, the US Ambassador to the United Nations said Iran must understand that it will face 'tangible and painful' consequences if it does not address international concerns.
John Bolton warned that a failure by the UN Security Council to address the issue would damage its credibility.
