Russia's President Vladimir Putin attends a meeting with members of the United Russia party in Moscow, Russia, September 6, 2016. REUTERS/Vasily Maximov/Pool

Actors George Clooney (L-R) and Don Cheadle and The Sentry Co-founder John Prendergast discuss The Sentry's investigation of the role of national corruption in the ongoing humanitarian crisis in South Sudan during a news conference at the National Press Club in Washington, U.S. September 12, 2016. REUTERS/Jonathan Ernst

Smoke rises over a damaged site as Civil Defence members try to put out a fire after an airstrike on al-Jalaa street in the rebel held city of Idlib, Syria. REUTERS/Ammar Abdullah

George Clooney (C), with fellow actor Don Cheadle (R) and The Sentry investigative journalist Brian Adeba (L), discuss The Sentry's investigation of the role of national corruption in the ongoing humanitarian crisis in South Sudan during a news conference at the National Press Club in Washington, U.S. September 12, 2016. REUTERS/Jonathan Ernst

A civil defence member carries an injured girl after an airstrike in the rebel-controlled city of Idlib, Syria. REUTERS/Ammar Abdullah

Civil defense members rest amid rubble of damaged buildings after an airstrike on the rebel-held Tariq al-Bab neighborhood of Aleppo, Syria. REUTERS/Abdalrhman Ismail

Civil defense members search for survivors under the rubble at a site hit by airstrikes in the rebel-controlled town of Ariha in Idlib province, Syria. REUTERS/Ammar Abdullah

A rebel fighter walks next to a tank in Jubata al-Khashab, in Quneitra countryside, Syria September 11, 2016. REUTERS/Alaa Al-Faqir