BEIRUT — U.S.-backed fighters captured a village in northern Syria on Saturday from members of the Islamic State group, bringing them closer to cutting a road linking two major IS-held cities in the country and closing in on the extremists’ de facto capital.

The push came as Turkish Prime Minister Binali Yildirim warned that if the predominantly Kurdish force eventually entered the city of Raqqa it will have negative effects on the relations between Ankara and Washington.

The Kurdish-led Syria Democratic Forces has been on the offensive toward the city of Raqqa since November. Still, once they approach the city the battle is expected to be bloody and long since the extremists have set up fortifications and have thousands of battle-hardened fighters.

Iraqi forces have been trying to capture Mosul since October and the extremists still hold the western half of the city.

The Britain-based Syrian Observatory for Human Rights and the SDF said Saturday that the predominantly-Kurdish force captured the village of Jawees.

The Observatory said SDF fighters are getting close to cutting the road that the extremists use to travel between Raqqa and f Deir el-Zour.

SDF fighters now control most of the villages and towns north of Raqqa and are gaining ground in eastern areas. The loss of Raqqa would be a major blow to the extremists since it was one of the first cities they fully controlled before declaring a caliphate in June 2014 in large parts of Syria.

Yildirim was quoted by the state-run Anadolu new agency while on a flight in Germany as saying that Turkey has made an offer regarding “saving Raqqa” from IS, adding that it will not be correct to move in with Kurdish fighters.

In August, Turkish troops rolled over the border to help Syrian opposition forces battle IS and halt the advance of U.S.-backed Syrian Kurdish fighters.