ISTANBUL (Reuters) - Turkey said on Tuesday it could expand its military mission in Syria to two other provinces, potentially bringing its forces into confrontation with U.S.-backed Kurdish fighters that Ankara considers its enemies.

Turkish troops have operated an “observation mission” in rebel-held territory in Syria’s northwestern Idlib province, under a deal with Damascus allies Russia and Iran to help reduce fighting between insurgents and government forces.

“It’s been considered that the observation mission of the Turkish armed forces in the Idlib de-escalation zone is continuing successfully, and such a mission being performed near Western Aleppo and Afrin would provide a real environment of peace and safety,” Turkey’s National Security Council said in a statement.

Ankara, which has long backed rebels fighting to overthrow President Bashar al-Assad, has toned down its demands that Assad leave power. It now says its main concerns in Syria are combating both Islamist militants and Kurdish fighters it considers allies of the Kurdistan Workers’ Party (PKK) which has fought a decades-long insurgency in southeastern Turkey.

Earlier this month, Turkish President Tayyip Erdogan said that Turkey needed to clear the Afrin region of northwest Syria of Kurdish YPG militia fighters as the military operation in Idlib province is largely complete.

The Kurdish YPG is the main element in a U.S.-backed force that Washington has assisted with training, weapons, air support and help from ground advisers in the battle against Islamic State. Washington’s support for the YPG is a bone of contention between the United States and Turkey, which are allies in NATO.