US: S-300 to Syria would be 'serious escalation'

US State Department spokeswoman Heather Nauert commented on Tuesday on Russia’s delivery of S-300 missile systems to Syria.

“I saw that report. I cannot confirm that that is accurate. I hope that they did not. That would be a – I think sort of a serious escalation in concerns and issues going on in Syria, but I just can’t confirm it, so I don’t have anything more for you on that right now,” said Nauert when asked about the subject at her daily press briefing.