RAQQA, Syria, Oct 8 (Reuters) - A final assault on Islamic State in Syria's Raqqa should begin on Sunday night, a field commander for the Syrian Democratic Forces (SDF), backed by a U.S.-led coalition, said on Sunday.

The assault would focus on the area around the stadium and attempt to surround it, the field commander, Ardal Raqqa, told Reuters in the city.

The spokeswoman for the SDF campaign in Raqqa, Jihan Sheikh Ahmad, said in a statement on a website for the campaign that it would announce the liberation of Raqqa "in the coming few days".

(Reporting By John Davison in Raqqa and Tom Perry; Writing by Angus McDowall in Beirut; editing by John Stonestreet)