U.N. Secretary General Kofi Annan urged the United States again on Friday to enter direct talks with Iran to ease a crisis over Iranian nuclear work after Washington vowed not to be drawn into "endless" dialogue.

United Nations Secretary-General Kofi Annan addresses the General Assembly of the United Nations in New York, in this May 2, 2006 file photo. [Reuters]

A senior U.S. official on Thursday ruled out U.S.-Iranian contact to help solve an international standoff over Tehran's nuclear work and said sanctions must be part of a new carrots and sticks offer to try to curb Iranian atomic activity.

"I have ... stated very clearly both in private contacts with the American administration and publicly that I think it is important that the United States come to the table and join the European countries and Iran to find a solution," Annan said at a Vienna summit of European Union and Latin American countries.

"(This is) because I really believe that as long as the Iranians have the sense they are negotiating with the Europeans ... and what they discuss with them will have to be discussed with the Americans and then (brought) back again to them..., they will not put everything on the table," Annan said.

Annan made a similar suggestion on U.S. public television last week. He has long been pushing for a diplomatic solution to avoid a resort to U.N. sanctions or even military action, a last-resort option mooted by the United States and Israel.

"I've asked all sides to lower their rhetoric and intensify diplomatic efforts to find a solution," Annan told reporters.

"I'm happy that the (Security Council) discussions seem to have led to a situation where everyone agrees that not only should one come back to the table and negotiate but there should be a comprehensive package proposed for discussions by all."

In the latest effort to resolve the crisis, Britain, France and Germany, with backing from the United States, Russia and China, are to unveil in the next 10 days a package of inducements and penalties for Iran.

While Iran insists it wants only to enrich uranium as nuclear energy for its economy, the West suspects that program could be a front for an atomic bomb project.