UNITED NATIONS (Reuters) - A report by United Nations chemical weapons experts will likely confirm that poison gas was used in an Aug 21 attack on Damascus suburbs that killed hundreds of people, UN Secretary-General Ban Ki Moon said on Friday.

"I believe that the report will be an overwhelming, overwhelming report that chemical weapons (were) used even though I cannot publicly say at this time before I receive this report," Mr Ban said at a UN meeting.

He was referring to a report by the UN expert team led by Ake Sellstrom of Sweden. Mr Ban also said that Syrian President Bashar al-Assad "has committed many crimes against humanity," though he did not say whether it was Mr Assad's forces or rebels who used chemical toxins in the Aug 21 attack.