Israeli Prime Minister Ehud Olmert warned in Los Angeles yesterday that Iran's efforts to develop nuclear weapons would lead to unprecedented unrest in the Middle East and beyond.

"If Iran achieves the ability to produce nuclear weapons, as we know it is seeking to do, we will enter a new era of instability unlike any the world has ever seen," Olmert told a gathering of Jewish leaders from around the world.

"We cannot afford to wait. We must all speak with one voice. No longer can the international community afford to hesitate, contemplate or waver in its dealing with this defiant state," he told the United Jewish Communities' 2006 General Assembly at the Los Angeles International Convention Center.

"No longer can we allow Iran to defer the demands of the international community without consequence," he said in his speech entitled "The New Front Lines: Facing the Future Together."

"We cannot tolerate -- we will not tolerate -- those who challenge Israel's right to exist while actively seeking to develop a catastrophic weapon to fulfill their goals," Olmert said.

Iran has denied accusations that it is developing nuclear weapons. It insists that its nuclear program is for peaceful means.

Olmert came from Washington, where he met with President George W. Bush at the White House to discuss measures to curb terrorism and bring peace to the Middle East as well as ways to encourage other nations to persuade Iran to abandon its nuclear program.

About 4,000 participants are taking part in the four-day assembly which started on Sunday. Being held in Los Angeles for the first time since 1982, the assembly is the largest annual gathering of Jewish leaders from North America, Israel and other parts of the world.

The assembly, sponsored by the United Jewish Communities which is the country's second largest charity, represents 155 Jewish Federations and 400 communities across North America.