Diplomats from six countries held talks in Berlin today on ways to get Iran to halt its disputed uranium enrichment programme.
The meeting was attended by US Under-secretary of State Nicholas Burns and included representatives from Britain, China, France, Russia and host Germany.
German officials said the meeting would seek to prepare for another round of talks between EU Foreign policy chief Javier Solana and Iranian nuclear negotiator Ali Larijani.
The six countries have been trying to get Iran to stop its programme to produce enriched uranium, which can be used for nuclear weapons or power plants depending on the level of enrichment.
The United States says Iran is trying to make nuclear weapons, while Iran says its programme is peaceful.
Mr Burns said that Iran, already under UN sanctions, could face moves toward tighter sanctions if it does not yield by the time of the Group of Eight summit in Heiligendamm in June.