Russia announced on Tuesday that it has completed the delivery of the S-300 air defense systems to Syria. "The work was finished a day ago," Defense Minister Sergei Shoigu said, adding that the system would help improve the security of Russian military personnel in Syria. Shoigu said in televised remarks that Moscow has delivered four S-300 launchers along with radars and support vehicles. It will take three months to train Syrian personnel to operate the system. Russia announced last month that it would provide the S-300s after the downing of a Russian plane by Syrian regime forces responding to an Israeli air strike, a friendly fire incident that stoked regional tensions. Russia decided to supply the system to Syria despite Israeli objections after Moscow accused Israel of indirectly causing the downing of the Russian military jet. The White House previously said it hoped Russia would reconsider the move, which US National Security Adviser John Bolton called a "significant escalation" of Syrias seven-year-old war.