Kharazi said the key was for Iran to find a "mechanism" to reassure the EU it is not trying to make nuclear weapons and "we are hopeful it would lead to a very fruitful agreement," the Iranian foreign minister told a press conference.

In a separate press conference, also in Budapest, Juncker said the key was for "Iran to step away from direct access to nuclear weapons."

The EU thinks it can "convince Iran... via the channels of negotiations in the next couple of weeks," Juncker said.

Kharazi is to visit Luxembourg later Tuesday.

"The discussions (in Luxembourg) will broach the European Union's relations with Iran, bilateral relations as well as recent negotiations in Geneva on Tehran's nuclear program," Luxembourg said in a statement.

Kharazi will be accompanied by deputy foreign minister Hamid Reza Asefi.

Iran on Sunday rejected a European offer under which it would give up construction of a heavy-water reactor, which can be used to make nuclear weapons material, in exchange for a light-water reactor offered by the Europeans.

EU negotiators Britain, France and Germany are trying to convince Iran to dismantle a uranium enrichment program the United States says is part of covert atomic weapons development, in return for economic and political rewards.

New US Secretary of State Condoleezza Rice last week urged European negotiators to take a tough line with Iran and warned Tehran of UN sanctions if it refuses to renounce its suspected nuclear weapons program.