Iran is a sponsor of terrorism and should realise it must not obstruct progress towards Middle East peace, UK Prime Minister Tony Blair has said.
Iran says its nuclear regime is peaceful
His words to MPs come after President George Bush branded Iran "the world's primary state sponsor of terror".
Mr Blair stressed the importance of the European Union's talks with Tehran over its nuclear activities and said it was important it fulfilled its obligations.
Iran says its nuclear programme is aimed at generating electricity.
The UK premier told the House of Commons liaison committee on Tuesday he agreed with President Bush's criticisms of Iran.
"It certainly does sponsor terrorism, there is no doubt about that at all," he said.
"I hope very much that if we can make progress in the Middle East that Iran realises it has an obligation to help that, not hinder it."
The US has refused to rule out a military strike on Iran, but has said it will try to resolve the dispute by diplomatic means.
Secretary of State Condoleezza Rice last week said military action was not on the agenda "at this point".
Mr Blair was asked if anybody would believe him were he tell Parliament that action was needed against Iran because it had weapons of mass destruction.
He replied: "I'm not saying that and, secondly, it depends what the evidence base is."
He also defended his record before the Iraq war, saying the Iraq Survey Group had reported weapons scientists had been ready to restart work.
Mr Blair said it was a good sign that the US and Europe were working together on the issue.
And he warned Iran and Syria that they would make a "very severe miscalculation" if they thought they could reduce the chances of an attack on themselves by allowing insurgents to cross into Iraq to weaken US troops.