United Nations Secretary-General Ban Ki-moon (L) and Ake Sellstrom, head of the UN mission that investigated the allegations of chemical weapons use in the Damascus suburbs, attend a press conference at the UN headquarters in New York, on Sept. 16, 2013. Chemical weapons were used at Ghouta, Syria, on Aug. 21 "on a relatively large scale resulting in numerous casualties, particularly among civilians and including many children," a UN report said Monday. [Photo/Xinhua]

United Nations Secretary-General Ban Ki-moon and Ake Sellstrom, head of the UN mission that investigated the allegations of chemical weapons use in the Damascus suburbs, attend a press conference at the UN headquarters in New York, on Sept. 16, 2013. Chemical weapons were used at Ghouta, Syria, on Aug. 21 "on a relatively large scale resulting in numerous casualties, particularly among civilians and including many children," a UN report said Monday. [Photo/Xinhua] 

United Nations Secretary-General Ban Ki-moon and Ake Sellstrom, head of the UN mission that investigated the allegations of chemical weapons use in the Damascus suburbs, attend a press conference at the UN headquarters in New York, on Sept. 16, 2013. Chemical weapons were used at Ghouta, Syria, on Aug. 21 "on a relatively large scale resulting in numerous casualties, particularly among civilians and including many children," a UN report said Monday. [Photo/Xinhua] 

United Nations Secretary-General Ban Ki-moon and Ake Sellstrom, head of the UN mission that investigated the allegations of chemical weapons use in the Damascus suburbs, attend a press conference at the UN headquarters in New York, on Sept. 16, 2013. Chemical weapons were used at Ghouta, Syria, on Aug. 21 "on a relatively large scale resulting in numerous casualties, particularly among civilians and including many children," a UN report said Monday. [Photo/Xinhua] 

United Nations Secretary-General Ban Ki-moon and Ake Sellstrom, head of the UN mission that investigated the allegations of chemical weapons use in the Damascus suburbs, attend a press conference at the UN headquarters in New York, on Sept. 16, 2013. Chemical weapons were used at Ghouta, Syria, on Aug. 21 "on a relatively large scale resulting in numerous casualties, particularly among civilians and including many children," a UN report said Monday. [Photo/Xinhua]