The top United States diplomat for the Middle East Anne Patterson said on Wednesday, most of the air strikes carried out by Russia have "dangerously exacerbated" the war in Syria, hitting the “moderate Syrian opposition” and killing civilians, rather than targeting terrorists.
Speaking to the House Foreign Affairs Committee, Patterson said the offensives backed by Russia had forced at least 120,000 people out of their homes.
"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,"
She added saying that Russia's primary intent was to “preserve the regime".
More than 600 people have been killed including 186 civilians since Russia started its air campaign in Syria, according to the Britain-based Syrian Observatory for Human Rights (SOHR).
Russia has been one of the main supporters of the Syrian regime leader Bashar al Assad, since the beginning of the four-and-a-half year long civil war.
Moscow began its aerial campaign in Syria last month, claiming it would also battle DAESH terrorist group, as the country has carried out 1,300 air strikes so far.
Washington's latest rebuke to Russia comes as regime troops, backed by Moscow's support, managed to recapture a key road into the second largest city Aleppo from DAESH, on Wednesday.
Last week top officials from 19 countries including Turkey and Saudi Arabia attended a summit in Vienna, in order to discuss the future of Syria where more than 250,000 people have lost their lives and millions have been displaced since March 2011. The Syrian government or its opponents were not invited to the meeting, as another round of talks are set to take place in two weeks.