The UK, France and Germany will hold fresh talks with Iran over its nuclear programme, British Foreign Secretary Jack Straw has said.
The next round of talks could be the last chance to find a solution
Delegates will probably meet in Paris early next week, Mr Straw said.
The European Union has threatened to back a US call for UN sanctions if Iran resumes the programme.
The US accuses Tehran, which wants to make enriched uranium, of developing nuclear weapons. Iran insists its programme is for civilian use only.
Tehran suspended enrichment activities in November 2004 and began talks with Germany, France and the UK.
But Tehran recently announced that it would restart the process of enriching uranium, in a move that would violate last November's agreement.
Mr Straw said he could not predict the outcome of next week's talks.
"I hope but I cannot predict... [they] will be fruitful," he told reporters on a trip to Washington.
US Secretary of State Condoleezza Rice backed the European nations' action, but declined to predict the next move in the dispute with Iran.
Tehran has been offered economic, political and technological incentives for giving up its uranium enrichment activities, which the West fears might be used for military purposes.
Iran says it is entitled to enrich uranium, but is ready to offer guarantees that its nuclear programme will be exclusively for civilian purposes.
British Prime Minister Tony Blair has already threatened United Nations Security Council action against the Iranians.
France and Germany have said that any violation of the November 2004 agreement would have "consequences" for Iran.