"We wish the Europeans good luck. They have our full support. Full support," Under Secretary for Political Affairs Nicholas Burns told reporters on the sidelines of a Euro-Atlantic Partnership Council Security Forum meeting in the central Swedish town of Aare.

His comments came on the same day as the foreign ministers of Britain, France and Germany met with Iran's top negotiator Hassan Rowhani in Geneva for crucial talks aimed at avoiding an escalation of Tehran's standoff with the West over its nuclear program.

Iran's chief negotiator, Hassan Rowhani, told AFP Wednesday: "This meeting is the last chance to see if we can continue the negotiations with the Europeans... otherwise we will choose another way."

"We have very strong support for France, the UK and Germany in their efforts to negotiate a complete cessation and dismantling of all uranium sensitive nuclear fuel cycling activities," Burns said.

"Iran should not become a nuclear weapons power. We all agree on that," he added, refusing however to disclose any proposals currently being discussed at the Geneva meeting.

"They are meeting now so I don't think (it is) appropriate for us to comment a meeting whose results are unknown," he said.

The aim of the Geneva negotiations is to save an accord signed in Paris late last year, in which Iran agreed to suspend "temporarily" its uranium enrichment activities in exchange for talks with the European Union on nuclear, technological and commercial cooperation.