New US Secretary of State Condoleezza Rice has called on Europe to show "unity of purpose" with Washington in opposing Iran's nuclear programme.
Condoleezza Rice is aiming to mend relations with European allies
"Diplomacy can work" in resolving tensions over Tehran's nuclear ambitions, she said after talks with German Chancellor Gerhard Schroeder.
But Iran had to show it was prepared to live up to its obligations, she said.
The EU has tried to negotiate with Tehran over its nuclear activities, but the US has urged a tougher stance.
The US failed last year to get Iran reported to the UN Security Council to face possible sanctions.
France, Germany and the UK are now negotiating with Iran to turn a freeze on its nuclear enrichment activities into abandonment.
Ms Rice began her first overseas tour as US secretary of state in London.
In London, Ms Rice insisted that attacking Iran was not on the US agenda "at this point in time".
But in a BBC interview to be shown on Sunday's Breakfast with Frost programme, Ms Rice said Iran was the "chief funder of terrorism".
Iran was the key supporter of Palestinian "rejectionist groups" and the Hezbollah movement, which she said were "one of the most important barriers" to Middle East peace.
"Iran is a destabilising force in the international system," she said.
In Iran, state-run television said Ms Rice was continuing the American trend of "psychological warfare" against the Iranian people.
Diplomatic efforts by Britain, France and Germany to negotiate with the Iranian authorities were a response to international concerns over the programme, she said in Berlin.
RICE'S SEVEN-DAY TOUR
Fri: Meets UK's Tony Blair and Foreign Secretary Jack Straw in London; talks with Germany's Gerhard Schroeder in Berlin
Sat: Talks with leaders in Germany, Poland and Turkey; meets Russian foreign minister in Ankara
Sun: Meets Turkish government, then on to Israel
Mon: Sees Ariel Sharon in Jerusalem, then Mahmoud Abbas in West Bank
Tue: Meets Silvio Berlusconi in Rome, then delivers speech in Paris
Wed: Talks with French ministers, then on to meet Nato and EU officials in Brussels and Luxembourg
Thurs: Returns to Washington
"I really do hope that the Iranians will take the opportunity that is being presented to them," she said.
Ms Rice's week-long tour of Europe and the Middle East includes talks with the Israeli and Palestinian leaders.
During the rest of the trip, Ms Rice is expected to give a staunch defence of President George W Bush's stated aim of spreading freedom and democracy around the world in what is seen as a bid to mend relations with nations opposed to the Iraq war.
Ms Rice will round off the trip by making a major speech on US-EU relations in Paris.