ROME - Secretary of State John Kerry said Thursday the transfer of advanced missile defense systems from Russia to Syria would be a "destabilizing" factor for Israel's security.
Kerry said the U.S. has expressed concerns about what such defensive systems in Syria would mean for Israel's security. He wouldn't address what the missiles might mean for Syria's civil war.
He spoke to reporters in Rome after the Wall Street Journal reported that Russia was preparing to sell the weapons to President Bashar Assad's regime.
Israeli officials said they have asked Russia to cancel the imminent sale to the Assad regime of advanced ground-to-air missile systems.
Such weapons would enhance the Syrian government's defensive ability and make it even harder for the U.S. and other governments to consider even the possibility of trying to enforce a no-fly zone in the country or otherwise intervening militarily.
Russia rarely comments publicly on arms sales or transfers, and there has been no official word on the deal in Moscow.
Even before Syria's 2011 uprising, the Israelis warned about a sale of S-300 batteries - which can target manned planes, drones and incoming missiles. Moscow had held off on the deal under persistent U.S. and Israeli pressure.
The S-300 would be a state-of-the-art upgrade for Syria's aging Soviet-supplied defense system, which was easily circumvented in 2007 when Israeli jets bombed a suspected nuclear reactor site along the Euphrates River in northeastern Syria.
And it would only add to reservations in the United States and other Western nations about a more forceful, military intervention to end the war. With the advanced aircraft interception technology, Syria would be able to present a far more robust defense than Moammar Gadhafi's Libya offered two years ago.
The Wall Street Journal put the deal at $900 million for a package of four batteries, six launchers and 144 operational missiles. The missiles have a range of 125 miles, it reported, citing the Israeli-provided information, adding that the materiel would start arriving over the next three months.
Russia remains the Syrian government's most powerful international ally.
Kerry met earlier this week with President Vladimir Putin and Foreign Minister Sergey Lavrov in Moscow to find a path forward. Kerry and Lavrov announced afterward that they would convene an international conference in the coming weeks to try to bring representatives of the Assad regime and the opposition to the negotiating table.
The enhanced Russian military support, if confirmed, would fly in the face of American claims that Moscow is demonstrating a new cooperativeness.
Moscow, with China, has repeatedly foiled Washington on Syria, blocking three U.N. Security Council resolutions against the Assad regime. It's unclear how its recent calculus has changed, even as U.S. officials point to statements by Lavrov and other Russian officials showing less support for Assad's continued leadership.
Moscow has been the source of most of Syria's military hardware since Assad's father and predecessor, Hafez, courted the Kremlin decades ago.
It has provided Syria with 36 Pantsyr mobile surface-to-air missile systems and at least eight Buk-M2E mobile SAMs. The Pantsyrs are considered particularly effective against attacking aircraft and feature a combination of 30mm cannons paired with a radar and anti-aircraft missiles on the same vehicle.
And other obsolete systems have been upgraded, and Kerry's predecessor, Hillary Rodham Clinton, sparked controversy last year when she accused the Russians of preparing to deliver attack helicopters.
Russians officials have insisted to their American counterparts that they are only honoring old contracts that are nearing expiration.