A US-backed operation to liberate Syria’s Raqqah from Daesh started on Friday night, Turkish Prime Minister Binali Yildirim announced.

Axar.az reports citing AA, ddressing the representatives of media outlets in capital Ankara late on Saturday, Yildirim said the United States informed Turkey regarding the operation before it started.

Yildirim reiterated Turkey's disapproval to the US method of conducting the Raqqah operation and said that the US reassured the weapons used by the PKK/PYD in Syria will not be a threat to Turkey.

"They [the US] told us that it was not an option but an obligation [to cooperate with PYD/YPG in Raqqah operation] and that the tactical cooperation with them would not be maintained for long after the [Raqqah] operation."

The difference between Washington and Ankara on Syria mainly derives from how they regard the armed groups in the region.

The Turkish government considers the PYD/YPG to be the Syrian offshoot of the PKK, a designated terrorist organization by Turkey and the U.S.

However, the U.S. does not view the PKK/PYD similarly, instead relying on the group extensively in the battle against Daesh in northern Syria. The YPG-backed Syrian Democratic Forces have been Washington's principal partner in the anti-Daesh fight.