"It will say that there was a chemical massacre," Fabius told French radio. The inspectors left Syria on August 31 after collecting samples as part of their probe into an alleged August 21 chemical weapons attack in a suburb of the Syrian capital.

But the key question — who deployed them — will not be addressed.

Under the agreement reached between the UN and the Syrian government, the mandate of the inspectors is to determine if chemical weapons were used, not by whom.

Still, the report is expected to be valuable in establishing once and for all whether chemical weapons were used in the early morning hours of August 21 in the eastern Damascus suburb of Ghouta.

The US president also said sarin gas was used in the attack, citing hair and blood samples studied by the US.

On that claim, Dan Kaszeta, a chemical weapons expert and former officer in the US army's chemical corps, said he was not so sure.

Alleged victims in videos posted on social media websites fail to show the telltale signs of sarin exposure, including contracted pupils and presence of bodily fluids, indicators of sarin use, Kaszeta said.

Although their mandate and UN protocols limit the questions that the inspectors address, the report is expected to put forward enough data for others — the UN general assembly, the security council and their member governments — to assign blame and take appropriate action.

NJF/NJF