By Louis Charbonneau
UNITED NATIONS (Reuters) - A report by U.N. chemical weapons experts will likely confirm that poison gas was used in an August 21 attack on Damascus suburbs that killed hundreds of people, U.N. 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," Ban said at a U.N. meeting.
He was referring to an eagerly awaited report by the U.N. expert team led by Ake Sellstrom of Sweden.
U.N. spokesman Farhan Haq said that Ban does not have Sellstrom's report yet. Ban has said previously, however, that he was in contact with Sellstrom and had urged him to expedite his conclusions.
Sellstrom is to travel to New York this weekend to deliver the report and brief Ban, said diplomats, speaking on the condition of anonymity.
The United States said on Friday it was confident that the U.N. report would say chemical weapons were used in Syria.
France's U.N. ambassador, Gerard Araud, told reporters that Monday is the tentative date for Ban to present Sellstrom's report to the Security Council and other U.N. member states.
Ban also said on Friday that Syrian President Bashar al-Assad "has committed many crimes against humanity," though he did not say whether it was Assad's forces or rebels who used the chemical weapons in the August 21 attack.
While Sellstrom's report will not explicitly pin the blame on either side, diplomats say the facts they gathered could suggest which side in the 2-1/2 year civil war was responsible.
The United States and other Western powers blame forces loyal to Assad for the attack. Russian President Vladimir Putin asserts there is "every reason to believe" it was carried out by rebels.
Two Western diplomats said they strongly expect Sellstrom's report will confirm the U.S. view that sarin gas was used in the attack, which the United States says killed over 1,400 people, many of them children.
The diplomats added they expected the report would indirectly implicate the Syrian government. They declined to elaborate, but the details that the report could include are types of weapons used and trajectories.
Sellstrom's report could become a bargaining chip in talks between Russia and Western powers on conditions for Syria to give up its chemical weapons and the terms of a U.N. Security Council resolution on the matter.
(Additional reporting by Michelle Nichols; Editing by Vicki Allen and Philip Barbara)