Prime Minister Ehud Olmert warned on Thursday that Iran would have "a price to pay" if it doesn't back down from its nuclear ambitions, hinting broadly that Israel might be forced to take action.

Olmert didn't specifically threaten to cripple Iran's nuclear program in a military strike. But he said the Iranians "have to be afraid" of the consequences of their intransigence.

"They have to understand that if they object to every compromise, there will be a price to pay," Olmert said on the plane carrying him and his entourage back to Israel after a three-day trip to Moscow, where he met with Russian President Vladimir Putin.

Israel rejects Iran's claim that its nuclear program is peaceful, designed solely to produce energy. In the past, Israel has said it would not lead a campaign against Iran's nuclear program, and act in concert with world powers that are similarly worried about Iran's intentions.

But with Iran rejecting various compromise proposals and insisting on enriching uranium — a process key to developing nuclear weapons — Olmert been raising the stakes with increasingly defiant rhetoric.

Israel cannot reconcile itself to a nuclear Iran, he said, and "there comes a time when you have to do damage control."

"A red line must be drawn that cannot be crossed," he said, without specifying what that line was.

"Time isn't standing still," he added. "And perhaps there will be a need to do something in the future."