BEIRUT — A U.S. military spokesman says there remains still tough fighting ahead after U.S.-backed Syrian fighters linked up their eastern and western font lines in the northern city of Raqqa.

U.S. Army Col. Ryan Dillon said in an email to The Associated Press that although the Syrian Democratic Forces linked up their east and west axis on the southern edge of the city of Raqqa, this does not in fact cut the city in two.

Dillon says the significance is that the SDF, despite ISIS’ best efforts, have successfully battled across the entire city from both sides and have joined forces.

The U.S. spokesman says this shows the steady progress the SDF fighters are making against IS in the militants’ self-declared capital.

SDF fighters have been on the offensive to capture Raqqa since June. 6, under the cover of airstrikes by the U.S.-led coalition.