Dozens of US special operations forces will arrive in Syria "very soon," as promised by President Barack Obama's administration, a senior official said Sunday.

The troops will have the task of organizing local forces battling the self-proclaimed Islamic State in northern Syria, according to special envoy Brett McGurk.

"They will be going in very soon," McGurk told CBS television's "Face the Nation" program.

In late October, Obama authorized no more than 50 special operations forces to deploy to northern Syria in a non-combatant, advisory role to help coordinate local ground troops and anti-IS coalition efforts.

It marks the first official deployment of US troops on the ground in Syria since an international coalition formed to counter the violent extremist group.

The US troops will assist an Arab-Kurd coalition that includes the main Syrian Kurdish militia the People's Protection Units (YPG), Arab groups and Syriac Christians.

These local forces "have been doing a very successful operation," McGurk said.

"This is focused on isolating the capital of ISIL in Raqa."

He said they have retaken about 1,100 square kilometers (435 square miles) in the last two weeks and killed about 300 IS fighters.

The US-led coalition aims to "suffocate and strangle them in the core" of IS in Iraq and Syria through multiple coordinated offensives, McGurk said.

The coalition is also trying to cut off access for IS to the Syrian border in order to cut off the main access route between Raqa and the Iraqi city of Mosul, McGurk explained.