Moscow is sending an advanced anti-aircraft missile system to Syria, two Western officials and a Russian source said, as part of what the West believes is stepped-up military support for embattled President Bashar al-Assad.

The Western officials said the SA-22 system would be operated by Russian troops, rather than Syrians. The system was on its way to Syria but had not yet arrived.

“This system is the advanced version used by Russia and it’s meant to be operated by Russians in Syria,” said one of the sources, a Western diplomat who is regularly briefed on U.S., Israeli and other intelligence assessments. […]