The Times of Israel reports: The US State Department said Tuesday that it could not confirm Russia had delivered the S-300 air defense systems to Syria, but that it would be a “concern” if it had.

“I hope that they did not,” State Department spokeswoman Heather Nauert told reporters in Washington when asked about the Russian Defense Ministry announcement claiming the delivery of the S-300 to Syria had been completed. “That would be sort of a serious escalation,” Nauert said.

Russia announced last week that it would boost security measures in Syria following the downing of a Russian military plane by an S-200 missile by mistake, which Moscow blamed on nearby Israeli planes. On Tuesday, Russian Defense Minister Sergei Shoigu told President Vladimir Putin in televised remarks that four S-300 launchers along with radars and support vehicles had been delivered to Syrian troops.

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