Syrian air defenses pose formidable challenge for responding to use of chemical weapons
"It's certainly the kind of system that if delivered would increase the risks for Israel, the USA or anyone else would they want to intervene militarily," Wezeman said.
Separately, Syria also has obtained from Russia the mobile Bastion-P land-based coastal defense systems, including Yakhont anti-ship missiles capable of sinking large warships, including aircraft carriers.
Russia has stood by Damascus since the uprising against Assad began in March 2011, shielding it from U.N. sanctions and continuing to supply the Syrian military with air defense components. Its support has not faded, even as the death toll in the conflict passed 70,000.
In February, Anatoly Isaikin, the head of the state arms trading agency Rosoboronexport, said that since there are no sanctions against shipping weapons to Syria, Russia was still fulfilling its contract obligations.
"These aren't offensive weapons," he said. "We are mostly shipping air defense systems and repair equipment for various branches of the military."
Like all of the Syrian military, the country's air defense system undoubtedly has suffered damage since the conflict became a civil war. Rebels have captured large swaths of northern Syria and have made a bridgehead in the south along the border with Jordan. Hydroelectric dams, cities and military bases have fallen into rebel hands.
But the extent of the fighting's toll on Syria's air defenses is, like many things in the country, hard to gauge.
"There is plenty of evidence that the rebels have been able to capture or destroy such air defense systems, and that included also new equipment," Wezeman said, citing videos posted on the Internet. "There must be major holes in there in the system."
Israel appeared to find one in January when it hit an apparent convoy purportedly carrying anti-aircraft missiles to the Lebanese militant group Hezbollah.
After that airstrike, Syrian Defense Minister Gen. Fahd Jassem al-Freij said rebels had made Syrian air defenses across the country a focus of their attacks, hitting some with mortar fire while trying to seize others in order to incapacitate them.
In response, he said the Syrian leadership decided to station them all in one safe place, leading to "gaps in radar coverage in some areas."
"These gaps became known to the armed gangs and the Israelis who undoubtedly coordinated together to target the research center," he said.
Despite al-Freij's uncommonly frank remarks, Elias Hanna, a retired Lebanese general and a senior lecturer at the American University of Beirut, said Syria's air defenses were still in good shape and would provide a stiff challenge to any foreign intervention.
Most of the country's air defense weapons, radar and other equipment have been positioned along Lebanon's border and in the Syrian-controlled part of the Golan Heights because Israel, which captured part of the territory in the 1967 war, was long perceived as the biggest threat, he said.
Some defense systems are also deployed along the Syrian Mediterranean coast and substantial air defense system have always been stationed in and around the capital Damascus.
"If there was an attack now," Hanna said, "Syria would have an upper hand."
Associated Press writer Jim Heintz in Moscow and Lolita C. Baldor in Washington contributed to this report.
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