Russia will not scrap plans to deliver an air defence system to Syria despite Western opposition because it would help deter "hotheads" intent on intervention in the two-year-old conflict, the deputy foreign minister said on Tuesday.

It also accused the European Union of "throwing fuel on the fire" by letting its own arms embargo on Syria expire.

Israel and France had urged Moscow to refrain from sending high-precision S-300 missile systems to President Bashar al-Assad's government, which is battling a Western and Gulf Arab-backed insurgency.

Deputy Foreign Minister Sergei Ryabkov suggested they were useful in deterring intervention.

"We think this delivery is a stabilising factor and that such steps in many ways restrain some hotheads from exploring scenarios in which this conflict could be given an international character with participation of outside forces," he told a news conference.

Russian officials have not disclosed whether S-300s have actually been sent to Syria and Ryabkov would not specify.

"I can't confirm or deny that these deliveries have taken place, I can only say that we will not disavow them," Ryabkov said. "We see that this issue worries many of our partners but we have no basis to review our position in this sphere."

Israeli Defence Minister Moshe Yaalon said on Tuesday that S-300s had not left Russia yet, seeming to contradict Israel's air force chief, who said last week the shipment of the missiles was on its way to Syria.

Russia has been Assad's most powerful ally during the 26-month-old conflict, opposing sanctions and blocking, with China, three Western-backed U.N. Security Council resolutions meant to pressure the government to stop fighting.

Moscow has vehemently opposed military intervention or arming Syrian rebels while defending its right to deliver arms to the government, its long-time client - though it says it has been supplying only defensive weapons under existing contracts.

Earlier Ryabkov said the European Union's failure to renew an arms embargo on Syria would undermine the chances for peace talks that Moscow and Washington are trying to organise.

"The European Union is essentially throwing fuel on the fire of the conflict," he repeated at his news conference. - Reuters