U.S. President George W. Bush threatened on Tuesday to seek more sanctions against Iran for its nuclear program.

"A group of countries can send a clear message to the Iranians, " Bush said, referring to a new proposal from Britain, China, France, Germany, Russia and the United States.

"And that is: we're going to continue to isolate you, we'll continue to work on sanctions, we'll find new sanctions if need be if you continue to deny the just demands of a free world, which is to give up your enrichment program," Bush told a press conference after a summit meeting with European Union (EU) leaders.

"Iran with nuclear weapons will be incredibly dangerous for world peace," he warned.

The new proposal will be presented soon to Iran by EU foreign and security policy chief Javier Solana.

Bush said Solana's message is that there is a better way forward for Iran than the current way that has led to isolation.

"It's their (Iran's) choice to make. They can either face isolation, or they can have better relations with all of us," Bush said.

He said Iran must verifiably suspend uranium enrichment, a process that can produce materials for both nuclear energy and nuclear weapons.

Bush said Iran "can't be trusted with enrichment" as it had ignored the UN nuclear watchdog, the International Atomic Energy Agency.

The United States and the EU claim that Iran intends to produce nuclear weapons while Tehran insists that its nuclear program is for peaceful purposes only. The UN Security Council has passed several resolutions, imposing sanctions on Iran.

In a declaration for the EU-U.S. summit, leaders urged Iran to suspend uranium enrichment and cooperate in the fight against terrorism.

"We expect Iran to comply with its international obligations concerning its nuclear activities, including the full and verifiable suspension of enrichment and full cooperation with the IAEA," reads the document.

The leaders said a "mutually satisfactory, negotiated solution" remains open to Iran, adding that they are ready to supplement current sanctions with "additional measures."

The EU and U.S. leaders also expressed concern over Tehran's alleged support for terrorism.

"We call upon the government of Iran to cooperate in the fight against terrorism. We reiterate our concern about Iran's regional policies, especially its continued support for terrorist organizations, and call on Iran to play a responsible and constructive role in the region," reads the declaration.