The jihadists, who conquered vast stretches of Iraq and Syria in 2014, have lost all but a pocket of land in Syria's eastern Deir Ezzor province between the Euphrates river and Iraqi border, though they remain present in the Syrian desert.

Using an Arabic acronym for IS, Lecointre predicted "the end of the physical caliphate of Daesh before the end of the year, probably late autumn".

France is part of the US-led coalition that has been fighting IS since 2014 and is now supporting Kurdish and Arab fighters of the Syrian Democratic Forces as they battle to oust the jihadists from their last holdout.

"Once the physical caliphate has fallen... we will pose the question of how to reconfigure Operation Inherent Resolve," Lecointre said of the coalition.

Speaking to reporters, the general pledged to downscale the French troop contingent -- currently more than 1,000-strong -- "as soon as I can".

The Syrian conflict has become increasingly complex since it grew out of anti-government protests in 2011, drawing in other major powers including Russia and Turkey.