WASHINGTON, October 3. /TASS/. The United States would view the deployment of Russia’s S-300 surface-to-air missile systems as an escalation, but it is yet to receive the official confirmation of the delivery, US Department of State Spokesperson Heather Nauert told reporters on Tuesday.

"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," she said.

Russian Defense Minister Sergei Shoigu said on Tuesday Russia had supplied Syria with 49 pieces of equipment as part of delivery of the S-300 air defense system meant to boost security of the Russian taskforce in that country.

"In conformity with the presidential decision, we have begun to carry out a number of measures to reinforce Syria’s air defense systems in order to ensure better protection for our servicemen. We have completed the delivery of S-300 systems. It included 49 pieces of equipment, including radars, control vehicles and four launchers," he told a Russian Security Council meeting chaired by President Vladimir Putin. According to the minister, the delivery was finished a day ago.