Turkish President Recep Tayyip Erdogan said Sunday his country may take further action against Kurdish militants in Iraq and Syria, as US -backed forces in Syria closed in on the last neighborhoods of a former stronghold of Daesh (ISIS).

Erdogan on Saturday repeated his call to the U.S.to cease its support of Syria’s Kurdish People’s Protection Units (YPG), which Turkey views as a prescribed terror organisation.

On 28 April, US troops visited the border areas between Rojava and Turkey to inspect the Kurdish areas bombed by the Turkish Army. Armored vehicles display US flags. Kurdish officials describe USA troop movement as “buffer” between them and Turkey.

Turkey last week bombed targets of the Kurdish Peoples’ Protection Units (YPG) in Syria, earning the wrath of its North Atlantic Treaty Organisation ally Washington, that said that the Combined Air Operations Centre received less than one-hour notice of the strikes. “If we are against global terrorism, then we need to tell them [U.S.] about these issues”.

In the meantime, Turkish President Recep Tayyip Erdogan has remained steadfast as he said that Turkey’s operations would continue “until the last terrorist is eliminated“.

Footage shot Friday night shows armored vehicles and personnel carriers on the road. The shelling hit near Darbasiya, a town in a Kurdish-controlled part of northeast Syria.

“We have forces in the entirety of northern Syria, the border is among the area where they operate“, said Navy Capt. Jeff Davis, a Pentagon spokesman.

The Turkish military said the April 25 attacks centered on Mount Sinjar in Iraq and Mount Karakoc in Syria. The Kurdish group in Syria said 20 of its fighters and media activists were killed in the strike, which was followed by cross-border clashes.

Erdogan hinted that his country was also ready to repeat its attacks in Sinjar, Iraq, to prevent it from turning into a base for the Kurdish militia.

US troops have since been seen patrolling the tense border.

Mark Toner, a State Department spokesman, said the USA was “deeply concerned” about the airstrikes, adding that the raids were “not approved” by the US -led coalition fighting against ISIS. Although the information did not specify civilian casualties, they indicated that there were continuous gun attacks on rural areas in various areas, a situation that aggravates the confrontation in the region, where the Kurdish Self-Defense Forces hold positions.

Pictures posted by pro-Kurdish activists on Twitter show military convoys flying USA and YPG flags passing through the mostly Kurdish-controlled city of Qamishli.

The patrols, which began Friday, are being led by US special operations forces, a USA official told CNN. Instead of working with the PYD, Turkey is pressing the U.S.to let its army join the campaign for Raqqa, ISIL’s self-proclaimed capital.

The Trump administration fired 59 cruise missiles at a Syrian air base in central Syria in the wake of the attack, marking the first time the US has directly struck Assad’s forces during the country’s six-year civil war.

Erdogan said the sight of American flags in the convoy alongside YPG insignia had “seriously saddened” Turkey.