Israeli Prime Minister Ehud Olmert made a surprise trip to Moscow on Thursday to discuss Iran's nuclear program with Russian President Vladimir Putin, who just returned from talks with Iranian leaders in Tehran.

The two leaders also were expected to discuss a reported arms deal that Russia is to sign with Syria, and Russia's role in Israeli-Palestinian peacemaking efforts.

Olmert's visit, expected to last just a few hours, was announced only after Putin had returned from Iran, where he vowed Tuesday to support Iran's pursuit of nuclear energy and warned "outside forces" — hinting at the United States — against using force against Tehran.

Olmert "will be very clear on the Israeli position that in no way can Iran achieve nuclear capability, that Iranian nuclear capability threatens the world, including Russia," Israeli government spokeswoman Miri Eisin said Thursday.

In announcing the trip Wednesday, Eisin said it had been scheduled several days earlier.

Israel's Yediot Ahronot newspaper said Olmert would give Putin an "unequivocal message."

"In a situation in which Iran has nuclear weapons and Syria has sophisticated weapons from Russia, Israel will have to weigh its actions against these threats," the newspaper said.

Israel considers Iran to be a threat to its existence, while Russia is a major provider of technology for Tehran's nuclear program, which Washington and its Western allies suspect is directed at the development of nuclear weapons.

Putin's meeting with Iranian President Mahmoud Ahmadinejad was likely seen by both Iran and Israel as a show of support for a president who has called for Israel's demise.

President Bush said Wednesday he wanted to get a readout directly from Putin about his visit to Iran, and to know whether Putin "continues to harbor the same concerns" as Bush about Iran's nuclear program. He also issued a warning that a nuclear-armed Iran could trigger World War III.

Russia has used its clout as a veto-wielding U.N. Security Council member to water down two sets of sanctions against Tehran over its refusal to halt uranium enrichment — which can lead to the development of weapons. Moscow has since resisted a U.S. push for additional sanctions.

Israeli Foreign Minister Tzipi Livni said Wednesday a new sanctions resolution was warranted, and that the need previously to secure Russian and Chinese support "led to some compromises on the nature of the sanctions. I hope this will not (be) the case this time."

Putin sought to assuage both Iran and the West during his trip to Tehran, a delicate balancing act reflecting his reach for global clout and desire to preserve warm ties with a Middle Eastern ally without angering Washington.

While offering support for Iran's right to nuclear energy and warning against the use of force, Putin rejected Iranian pressure to set a firm startup date for the nuclear power plant Russia is building in Iran.

Putin also made an unspecified proposal concerning Iran's nuclear program to the country's supreme leader Ayatollah Ali Khamenei, Iran's state news agency IRNA reported. Officials close to hard-liners within Iran's ruling Islamic establishment said they believed the proposal involved a "timeout" on sanctions if Iran suspends uranium enrichment.

On Thursday, however, Iranian President Mahmoud Ahmadinejad said Putin "did not say any word" about the nuclear program during his meeting with the supreme leader, IRNA reported.

In addition to the nuclear situation, Olmert also was expected to address Israeli concerns about reported Iranian-funded arms deals in the works between Russia and Syria.

Yediot Ahronot reported that Russia plans to provide Syria with surface-to-air missiles and anti-aircraft missiles that it has never before sold to another country.

Russia disputes Israeli claims that Russian arms sold to Syria have made it to Hezbollah guerrillas in Lebanon. Moscow insists its weapons deals with Syria and Iran have complied with international law and have not disrupted the balance of power in the region.

Another possible item on the agenda could be last month's airstrike deep into Syria, in which the Israeli aircraft slipped past Russian-made Syrian air defense systems, hit their target and then left unchallenged.

Syrian President Bashar Assad has said Israel bombed an "unused military building" in the Sept. 6 raid. Israel has been extremely secretive about the affair and only recently relaxed censorship to allow journalists to report that Israeli aircraft attacked a military target deep inside Syria.

Eisin said Olmert and Putin would also discuss Israeli-Palestinian issues, stressing that Olmert "emphasizes the need to continue to sideline (the Palestinian militant group) Hamas."

Russia, a member of the Quartet of Mideast negotiators, argues that engagement is more effective than isolation. Moscow attracted the anger of Israel and Western nations by hosting the radical Islamic group's leadership for talks last year.

Olmert's visit was announced as Secretary of State Condoleezza Rice met Israeli and Palestinian leaders as part of preparations for a U.S.-hosted peace conference in November or December.

Rice was heading for London seeking support from Jordan's King Abdullah II for the conference after telling Israelis and Palestinians they have a new "moment of opportunity" to forge peace, despite the obstacles.