Dozens of US special operations forces will arrive in Syria "very soon", as promised by President Barack Obama's administration, a senior official says.
The troops will have the task of organising 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 on Sunday (local time).
In late October, Obama authorised no more than 50 special operations forces to deploy to northern Syria in a non-combatant, advisory role to help co-ordinate 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, 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 Raqqa."
He said they have retaken about 1100 square kilometres in the past 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 Raqqa and the Iraqi city of Mosul, McGurk explained.