The US and the EU yesterday sought to turn up the pressure on Iran to drop its nuclear enrichment programme by saying they were ready to go beyond a latest round of UN sanctions.
But President George W. Bush acknowledged the limits of US influence over Tehran and, in the twilight of his presidency, appeared resigned to leaving the standoff to his successor.
"I leave behind a multilateral framework to work on this issue," Mr Bush said after a US-EU summit at a Slovenian castle.
"A group of countries can send a clear message to the Iranians, and that is: We're going to continue to isolate you... we'll find new sanctions if need be, if you continue to deny the just demands of the free world, which is to give up your enrichment programme," he said.
He stopped short of repeating the US position that all options, including military action, remain open. "Now is the time for there to be strong diplomacy," Mr Bush said.
He met Slovenian leaders, who hold the EU's rotating presidency, as well as European Commission President Jose Manuel Barroso and EU foreign policy chief Javier Solana, who has led efforts to get Iran to scrap its enrichment programme.
Mr Solana is due to travel to Iran at the weekend to present a new offer by major powers of incentives for it to suspend the programme but he has played down prospects of a breakthrough.
"Iran with a nuclear weapon would be incredibly dangerous for world peace," Mr Bush said before setting off for Germany.
He is also due this week to visit France, Britain and Italy. A summit statement said the US and EU were ready to deploy measures against Iran beyond existing UN sanctions.
All agree Iran should not be allowed to acquire nuclear weapons. Tehran insists the programme is for civilian purposes.
But it remained unclear how far the Europeans, who rarely echo Mr Bush's harsh rhetoric against Iran and have sometimes been reluctant to get tougher, would be willing to go. The UN Security Council has imposed three rounds of sanctions on Iran. Washington has pressed the EU to deny some Iranian banks access to the world financial system.
European External Relations Commissioner Benita Ferrero-Waldner told reporters after the summit: "We want to indeed show to Iranians that we mean it very seriously... (We are) particularly thinking of asset freezes."