But President George W. Bush acknowledged the limits of U.S. 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," Bush told a news conference after a U.S.-European Union 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 U.S. position that all options, including military action, remain open, suggesting that no drastic steps were likely before he leaves office. "Now is the time for there to be strong diplomacy," 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 drop its enrichment programme.
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Solana is expected to travel to Iran soon to present a new offer by major powers of incentives for it to suspend uranium enrichment, but he has played down prospects of a breakthrough.
"Iran with a nuclear weapon would be incredibly dangerous for world peace," Bush said before setting off for Germany.
He is also due this week to visit France, Britain and Italy. All have roles on the Iranian issue.
A statement released after the three-hour summit said the United States and EU were ready to deploy extra measures against Iran on top of existing U.N. sanctions.
All agree Iran should not be allowed to acquire nuclear weapons, a possible outcome of its uranium enrichment program. Tehran insists the program is strictly for civilian purposes.
But it remained unclear how far the Europeans, who rarely echo Bush's harsh rhetoric against Iran and have sometimes been reluctant to get tougher, would be willing to go.
