Fears grew of a foreign-fed arms race in Syria on Tuesday as European Union countries decided they could provide weapons to the rebels and Russia disclosed that it has signed a contract to provide Syria with sophisticated anti-aircraft missiles.

Either development would significantly raise the firepower in the two-year civil war that has already killed more than 70,000 people and sent hundreds of thousands fleeing the country, just as the key countries prepare for a major peace conference in Geneva that has been described as the best chance yet to end the bloodshed.

Russian officials criticized the EU decision Monday night to allow their arms embargo against Syria to expire, freeing its member countries to provide weapons for the outgunned rebels. Russia, which has been a strong supporter of the Syrian government, said the British- and French-driven decision undermined peace efforts.

Deputy Foreign Minister Sergei Ryabkov said Tuesday that Russia has signed a contract with the government of Syrian President Bashar al-Assad to provide it with state-of-the-art S-300 air defence missiles, which he said were important to prevent foreign intervention in the country. Ryabkov would not say whether Russia has shipped any of the missiles to Syria yet.

Ryabkov said Russia understands the concerns about providing such weapons to Syria, but believes that may "help restrain some hot-heads considering a scenario to give an international dimension to this conflict."

Israel delivers veiled warning over missiles

Israel's defence minister, meanwhile, signalled that his military is prepared to strike shipments of advanced Russian weapons to Syria, in a rare implied threat to Moscow.

Defence Minister Moshe Yaalon issued his warning Tuesday after the announcement from the Russian deputy foreign minister.

Israel has been lobbying Moscow to drop the sale, fearing the missiles would upset the balance of power in the region and could slip into the hands of hostile groups, including the Lebanese militant group Hezbollah, a close ally of the Syrian regime.

"As far as we are concerned, that is a threat," Yaalon told reporters when asked about the S300s.

"At this stage I can't say there is an escalation. The shipments have not been sent on their way yet. And I hope that they will not be sent," he said. But "if God forbid they do reach Syria, we will know what to do."

Since Syria's civil war erupted in March 2011, Israel has repeatedly voiced concerns that Syria's sophisticated arsenal, including chemical weapons, could either be transferred to Hezbollah, a bitter enemy of Israel, or fall into the hands of rebels battling Assad. The rebels include al-Qaeda-affiliated groups that Israel believes could turn their attention toward Israel if they topple Assad.

Israel has carried out several airstrikes in Syria that are believed to have destroyed weapons shipments bound for Hezbollah. Israel has not confirmed carrying out the attacks. The delivery of the Russian missiles to Syria could limit the Israeli air force's ability to act.

Syria criticizes expiry of arms embargo

EU diplomats have said Britain and France are considering providing equipment to the rebels, and Syrian neighbours Turkey and Lebanon risk being drawn into the conflict.

Ryabkov called the EU move to end its arms embargo "a manifestation of double standards" that will hurt the prospects for the Geneva talks, which are expected to happen in June.

In Damascus, a Syrian lawmaker on Tuesday also criticized the EU decision, saying that efforts to arm the rebels will discourage the opposition from seeking a peaceful solution to the conflict. The comments by Essam Khalil, a member of the parliament for the ruling Baath Party, were the first by a Syrian official.

U.S. Senator John McCain, meanwhile, made an unannounced visit to rebel forces in Syria, putting more pressure on Assad to seek a negotiated settlement.