According to a Russian diplomat, Syrian terrorists do not use weapons supplied by Russia to the Syrian government. He said that those terrorists were using weapons supplied by the United States and its allies.

Konstantin Kosachev, the chairman of the international committee of Russia’s Federation Council upper parliament house, believes that those who supply weapons to the opponents of Syrian President Bashar al-Assad are responsible for the political unrest in the country, Russia's Tass news agency reported.

"So, responsibility rests on those who supplies weapons to the opposition and these weapons are freely draining to terrorists," Kosachev said in an interview.

Kosachev’s comment comes as Russian President Vladimir Putin said at the summit of the Collective Security Treaty Organization in Dushanbe that no one would “manage to pass the buck” for the situation in Syria. Putin said that no one should blame Russia for the political crisis in the Middle Eastern country because Kremlin provided support to the Assad regime.

Washington, meanwhile, asked Kremlin to explain the reason behind Russia’s military build-up in Syria. U.S. Secretary of State John Kerry had a phone conversation with his Russian counterpart Sergei Lavrov, the third phone call Kerry made to Lavrov in the last 10 days.

"Secretary Kerry also reaffirmed the US commitment to fight ISIL (Islamic State) with a coalition of more than 60 countries, of which Assad could never be a credible member, and emphasized the US would welcome a constructive Russian role in counter-ISIL efforts," the BBC quoted a Washington statement.

Russia said that it provides support to Assad for fighting Islamic State group militants while White House spokesman Josh Earnest believes Russia’s support for the Syrian government is "a losing bet."