Children react after what activists said was shelling by forces loyal to Syria's President Bashar al-Assad near the Syrian Arab Red Crescent center in the Douma neighborhood of Damascus May 6, 2015. (Photo by Bassam Khabieh/Reuters)

The Syrian refugee folklore troupe Abu Rustom perform at a wedding show at Zaatari refugee camp in the Jordanian city of Mafraq, near the border with Syria February 20, 2017. The Syrian troupe is trying to keep its country's traditions alive by holding traditional dances and performing celebratory sword fights during weddings and other occasions, according to the troupe's leader. (Photo by Muhammad Hamed/Reuters)

Women, who are members of Saaed group, prepare food to be given out as Iftar meals for the poor and internally displaced Syrians during the month of Ramadan in Damascus, Syria June 18, 2016. Iftar (or Fatoor) is the evening meal when Muslims end their daily Ramadan fast at sunset. Muslims break their fast at the time of the call to prayer for the evening prayer. (Photo by Omar Sanadiki/Reuters)

Syrian President Bashar Al Assad watches as Pope John Paul II boards his plane at Damascus airport May 8, 2001 at the end of the Pontiff's four-day visit to Syria.

Members of the Al-Baraa bin Malek batallion, part of the Free Syria Army's Al-Fatah brigade, duck to the ground as they pull a man (R) who was shot by a sniper twice in the Bustan al-Basha district of the northern city of Aleppo on October 20, 2012. (Photo by Javier Manzano/AFP Photo)

Refugees and migrants try to find a place on an already full train headed for Serbia, near the city of Gevgelija, The Former Yugoslav Republic of Macedonia, on February 24, 2016. Refugees and migrants from Iraq and Syria continue to pass through Macedonia on their way to the European Union. (Photo by Georgi Licovski/EPA)

Men work at a makeshift oil refinery site in Marchmarin town, southern countryside of Idlib, Syria December 16, 2015. The refinery site, owned by Yousef Ayoub, 34, has been active for 4 months. Ayoub says that he gets the crude oil from Islamic State-controlled areas in Deir al-Zor province and Iraq. The price for a barrel of crude oil varies and is controlled by the Islamic State, but it is currently at $44 dollars per barrel, he said. (Photo by Khalil Ashawi/Reuters)

Syrians try to rescue a dead body under the debris of a collapsed building after Syrian and Russian army carried out an airstrike on opposition controlled residential area at Merce neighborhood of Aleppo, Syria on September 23, 2016. (Photo by Jawad al Rifai/Anadolu Agency/Getty Images)