WASHINGTON (AFP) – President George W. Bush Wednesday warned Iran must be barred from nuclear weapons to avoid the prospect of “World War III,” and dismissed suggestions of a US-Russia rift on the crisis.

Bush intervened hours after Russian President Vladimir Putin made a new proposal to end the nuclear crisis as he met Iranian President Mahmoud Ahmadinejad for landmark talks in Tehran.

Iran’s top nuclear negotiator Ali Larijani meanwhile revealed he would hold new talks with EU foreign policy chief Javier Solana on Tuesday in Rome to search for a solution to the atomic standoff.

Bush upped US rhetoric at a White House news conference, warning the world must do more to isolate the Islamic republic.

“We’ve got a leader in Iran who has announced that he wants to destroy Israel,” Bush said.

“So I’ve told people that, if you’re interested in avoiding World War III, it seems like you ought to be interested in preventing them from having the knowledge necessary to make a nuclear weapon.”

Iranian officials said Putin put forward a proposal to break the deadlock over Iran’s nuclear program during his exhausting and historic visit, but gave no further details.

Earlier, Putin and Ahmadinejad shook hands and smiled, as they met for talks in Tehran.

“I’m looking forward to getting President Putin’s read-out from the meeting,” Bush said.

“The thing I’m interested in is whether or not he continues to harbor the same concerns that I do,” Bush added.

Democratic Senator Barbara Boxer slammed Bush for his cataclysmic view about Russia, especially after he described Putin as a good man on their first encounter.

“I keep hoping the president will do the right thing, but he just seems to go down that cowboy path all the time,” she told reporters. “I don’t think he understands that his words have to be measured and it’s quite unfortunate.”

Putin also held talks with Iran’s supreme leader Ayatollah Ali Khamenei, and was quoted by state television as hoping for a “new page” in Moscow’s relations with the US foe.

Last week, Putin said after talks in Moscow with President Nicolas Sarkozy of France that Russia had no information Iran was trying to make a nuclear bomb.

“I look forward to having him clarify” those (comments), Bush said.

“Because when I visited with him, he (said he) understands that it’s in the world’s interests to make sure that Iran does not have the capacity to make a nuclear weapon.”

The Russian president also called during a summit with Caspian leaders for any prospect of foreign military action against Iran to be ruled out.

Washington refuses to renounce the military option, spurring speculation on the chances of a US strike, should diplomacy ultimately break down.

Hours after Putin left Iran, its archfoe Israel announced Prime Minister Ehud Olmert would visit Russia Thursday for what one official described as a “last-minute, urgent meeting.”

“The two intend to discuss a series of regional issues, including the peace process with the Palestinians, Iran’s threat and attempt to acquire nuclear weapons, and developments in the region,” Olmert’s office said.

Israel is one of the leading campaigners against Iran’s nuclear ambitions along with chief ally the United States, but is widely regarded as the Middle East’s sole if undeclared nuclear armed state.

Despite having failed to find a breakthrough in several meetings over the past year, Larijani said he was set for the new talks with Solana in Rome on Tuesday.

The key sticking point remains Iran’s refusal to suspend uranium enrichment, which the West fears could be diverted towards making a nuclear bomb.

Iran insists it only wants to generate electricity and has consistently refused to budge an inch on its right to the full nuclear fuel cycle but has been slapped with two sets of UN sanctions for its defiance.

Solana must report to major world powers Britain, France, Germany, Russia, China and the United States before mid-November on Iran’s willingness to give up uranium enrichment in exchange for political and trade incentives.

A senior US State Department official said on a visit to Brussels Wednesday that Washington could change its approach to developing a missile shield in central Europe if Iran were to suspend uranium enrichment.

“Our real concern is not Russia,” Assistant Secretary of State Daniel Fried said.

The shield is “intended against the major problem we see developing, which is Iran, and if that problem went away or attenuated we would obviously draw conclusions,” he said.