Update to this story.

(Reuters) – Syrian rebel commanders from the Islamic Front which seized control of bases belonging to Western-backed rebels last week are due to hold talks with U.S. officials in Turkey in coming days, rebel and opposition sources said on Saturday.

The expected contacts between Washington and the radical fighters reflect the extent to which the Islamic Front alliance has eclipsed the more moderate Free Syrian Army brigades – which Western and Arab powers tried in vain to build into a force able to topple President Bashar al-Assad.

The talks could also decide the future direction of the Islamic Front, which is engaged in a standoff with yet more radical Sunni Muslim fighters from the al Qaeda-linked Islamic State in Iraq and the Levant (ISIL).

A rebel fighter with the Islamic Front said he expected the talks in Turkey to discuss whether the United States would help arm the front and assign to it responsibility for maintaining order in the rebel-held areas of northern Syria.