U.S. Secretary of Defense James Mattis has said that the U.S. military will remain in Syria until the situation is resolved by the Geneva process.

Mattis said the presence of the United States in Syria has been approved by the UN as Washington is engaged in the fight against ISIS terrorists.

“You know, the UN said that ISIS — basically we can go after ISIS,” Mattis told reporters on Monday, responding to a question about the legality of the U.S. presence in Syria.

He said Washington’s presence in Syria was in order “to take them out,” stressing the importance of the Geneva settlement process so that the defeat of the terrorists “doesn't mean we just walk away and let ISIS 2.0 pop back around.”

This comes while Damascus has repeatedly criticized the U.S. presence in Syria, stressing any foreign military operation taking place without government approval would be considered an “illegal invasion”.

On the other hand, other countries such as Russia and Iran have been authorized by the Syrian government to play an active role in the fight against ISIS.

Syria has been grappling with a foreign-backed militancy 2011, when militants – backed by some regional and Western countries – poured into Syria to fight the Syrian government.

Hundreds of thousands of people have been killed and millions displaced since the onset of the conflict in Syria.