The United States said that Russia ' s air war in Syria had " dangerously exacerbated " the conflict, accusing Moscow of seeking to bolster President Bashar al - Assad ' s regime instead of targeting jihadists. Washington's latest broadside against Russian intervention in Syria came as government troops, emboldened by Moscow's support over the past month, recaptured from the Islamic State group a key road into second city Aleppo. It also came as Russian air force commander, Viktor Bondarev, said Thursday Moscow had sent anti-aircraft missile systems to Syria to back up its air campaign. "We sent there not just fighter planes, strike aircraft and helicopters but also anti-aircraft rocket systems," Bondarev told Komsomolskaya Pravda tabloid daily. He said that Russia made the decision to bring missile systems to Syria because "we took into account every possible threat." Bondarev said Russia has "more than 50 planes and helicopters" in Syria, "precisely the number we need. At the moment, we do not need more." Speaking to the House Foreign Affairs Committee, US Assistant Secretary of State for Near Eastern Affairs Anne Patterson said the offensives, backed by Russian air strikes, had displaced at least 120,000 people. "Russia's military intervention has dangerously exacerbated an already complex environment," she said. "Moscow has cynically tried to claim that its strikes are focused on terrorists, but so far, 85 to 90 percent of Syrian strikes have hit the moderate Syrian opposition and they have killed civilians in the process," Patterson said. Civilians have died in Russian strikes on civil defense crews, hospitals, centers for displaced persons and ambulances, she claimed. "We know that Russia's primary intent is to preserve the regime," she said. Regime forces launched major offensives in several parts of Syria after Russia began its intervention on September 30, with more than 1,300 air strikes carried out so far. "Despite our urging, Moscow has yet to stop the Assad regime's horrific practice of barrel bombing the Syrian people," Patterson said. She said the situation called for a "full court press to end the war and get to a political settlement." "The Russian deployments cannot be used to stiffen the Assad regime's resistance to a political transition."