Tel Aviv: The sale of S-300 air defence systems by Russia to Syria would be "destabilising" for the region, US Secretary of State John Kerry said.
"S-300 missiles coming from Russia, or other countries, Iranian missiles, are destabilising to the region," Kerry said.
"The United States is committed, not only in its defence of Israel, but in its concerns for the region to try to address this issue."
Russian Foreign Minister Sergei Lavrov said earlier this month that Russia would honour a deal with Syria to supply it with S-300 air defence systems.
"Those who do not plan aggressive actions against a sovereign state have nothing to worry about, because means of air defence - and this is clear from the name - are a purely defensive system required to repel air attacks," Lavrov said.
He said the deal was signed before Israel planes hit targets in Syria earlier this month.
S-300 is widely acknowledged by defence analysts as one of the world`s most advanced air defence systems.
An S-300 battery would "provide coverage of much of northern and central Israel if deployed in the south west of Syria for targets other than those at low altitude," said Douglas Barrie, an air warfare analyst with the London-based International Institute of Strategic Studies.
The sale of Russian weapons to Syrian President Bashar al-Assad`s regime has been a source of bilateral tension between Moscow and Washington, with US officials accusing Russia of arming a regime the US says is killing its own citizens in Syria`s raging civil war.
Washington has criticised Moscow for delivering advanced Yakhont anti-ship missiles to Damascus, and also called on Russia not to deliver overhauled helicopter gunships to the Assad regime.
Russia, however, has insisted that the deliveries are legal under international law and that it is not supplying Syria with offensive weapons which can be used to kill civilians.