People inspect the damage after a car bomb exploded and targeted a religious center in the rebel-controlled area of Maaret al-Numan town in Idlib province, Syria April 5, 2016. REUTERS/Khalil Ashawi

ANKARA (Reuters) - U.S. officials are discussing with the Turkish military and government how the moderate Syrian opposition can push Islamic State farther east in Syria, Washington’s ambassador to Ankara said on Thursday.

“We have had some progress in recent weeks as these groups pushed further east along the border,” Ambassador John Bass told a group of diplomacy correspondents. “We will continue to focus on that area,” he said.

Syrian rebel forces seized numerous villages from Islamic State near the Turkish border earlier this week. The offensive includes factions fighting under the banner of the Free Syrian Army that have been supplied with weapons via Turkey.

A sustained rebel advance near the Turkish border would erode Islamic State’s last foothold in an area identified by the United States as a priority in the fight against Islamic State.

“There is conversation with the Turkish military and government to talk about opportunities to intensify support to those groups and to push Daesh east from the current line,” Bass said, using an acronym for Islamic State.

The United States is not providing the Syrian Kurdish YPG militia, its close ally in the fight against Islamic State, with weapons or ammunition, Bass said. He said Washington is opposed to efforts by any Syrian group to change the demography of a region “under the guise” of fighting Islamic State.

Turkey has accused the YPG of “cleansing” towns of ethnic Arabs and Turkmen.

Bass repeated a call to the Kurdistan Workers Party (PKK) to lay down its weapons and cease attacks on Turkey. The PKK has waged a three-decade insurgency in Turkey and violence flared anew in July.

Ankara says the PKK, designated a terrorist organisation by Turkey, the United States and the European Union, is closely linked with the YPG.