“The coalition actively supporting the rebels as they advance to within a few kilometres of (its) weakening stronghold" of Dabiq, Brett McGurk, Washington's special envoy for the coalition, said in a Tweet.

Washington believes taking Dabiq could strike at Islamic State morale as it prepares to fend off expected offensives against Iraq's Mosul and Syria's Raqqa, the largest cities held by the jihadists.

The group has used Dabiq as a theological raison d’etre for fighting in Syria.

Isil named its main English-language propaganda magazine after the town, regularly writing about the significance of the battle for Dabiq in Islamic history.

"The spark has been lit in Iraq, and its heat will continue to intensify - by Allah's permission - until it burns the Crusader armies in Dabiq," Abu Musab al-Zarqawi, one of Isil’s founders, said in a 2015 issue of the magazine.