Russia has ended weeks of ambiguity and insisted that it will honor its deal to sell “game-changing” S-300 anti-aircraft systems to the Syrian government. The advanced, long-range surface-to-air weapons could deeply complicate any attempt by the US or Israel to intervene in the bitter civil war, which is now in its third year.

The angry statement out of Moscow Tuesday appeared to be a direct response to the lapse of the European Union’s arms embargo against Syria, which removes obstacles to providing lethal assistance to the Syrian rebels. Britain and France have been seriously considering arming the rebels.

Speaking to journalists in Moscow, Deputy Foreign Minister Sergei Rybakov said Russia considers it imperative to fulfill the three-year-old, $900 million contract to supply six batteries, with 144 S-300 missiles to Syria, despite Western objections.

Russia has argued all along that its arms deliveries to Syria involve the completion of “old contracts” signed before the civil war erupted, that they are completely legal since no United Nations sanctions have been declared against the regime of Mr. Assad, and that the arms delivered are purely of a “defensive” character.

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To this Mr. Rybakov added a fresh reason Tuesday, saying the S-300’s will help to “stabilize” the volatile Middle East region.

“We believe (S-300 sales) are to a great extent restraining some ‘hot heads’ from considering scenarios in which the conflict may assume an international scale with the participation of outside forces,” Rybakov said. “I can neither confirm, nor deny in what stage these deliveries are at… We understand all the concerns and signals sent to us from various states. We see that this issue worries many of our partners. We have no reasons to reconsider our position in this sphere,” he added.

Some Russian analysts say the S-300s are probably unlikely to turn up in Syria anytime soon, despite what Ryabakov says. For one thing, they say, the missile systems are big and sophisticated, and require teams of dedicated operators to take about a year of special training in Russia before they are qualified to use them. For another, transport into the Syrian war zone would be a logistical nightmare.

“It’s not only politically complicated to supply these missiles to Syria just now, it’s physically very difficult,” says Vadim Kozyulin, an expert with the PIR Center in Moscow, an independent think tank that specializes in security issues. “They would be very vulnerable to being destroyed while in transit, and I don’t doubt there are forces already thinking of doing that. In short, I don’t believe any S-300’s are going to make an appearance in Syria.”

The London Sunday Times quoted an unnamed Kremlin official two days ago as saying that Russian President Vladimir Putin and Israeli Prime Minister Benjamin Netanyahu agreed at a meeting earlier this month in Sochi that Russia would suspend the controversial deal in exchange for a halt to Israeli airstrikes against Syria.

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