Kurdish forces allied with the US issued a “general mobilization” call Wednesday in northeastern Syria amid worries of a “humanitarian catastrophe” from an expected invasion by Turkey.

Turkey has long threatened an assault on Kurdish fighters in Syria whom Ankara considers terrorists — but expectations for an attack rose after President Trump abruptly announced Sunday that US troops would be pulled from the area.

A pullout marks a dramatic shift in US policy that essentially abandons the Syrian Kurds, longtime US allies in the fight against ISIS in Syria.

Trump reacted to the developments in a tweet, saying: “Fighting between various groups that has been going on for hundreds of years. USA should never have been in Middle East. Moved our 50 soldiers out. Turkey MUST take over captured ISIS fighters that Europe refused to have returned. The stupid endless wars, for us, are ending!”

The Britain-based Syrian Observatory for Human Rights, a Syrian war monitoring group, reported Wednesday that people were fleeing the border town of Tal Abyad.

A Turkish official told Bloomberg News that the first Turkish troops have already crossed into northeastern Syria at two points along the border, near the border towns of Tal Abyad and Ras al-Ayn.

Journalists from the Associated Press on the Turkish side of the border reported seeing Turkish forces crossing into Syria in military vehicles, though there was no official word from either side that the offensive had begun.

Another Turkish official denied that the country had begun its operation against the Kurdish fighters.

“Reports in some media outlets stating that the operation has begun do not reflect the reality. Operation has not been launched yet,” the official told Agence France-Presse.

Defense Minister Hulusi Akar said earlier Wednesday that the military build-up along the southern border was continuing.

“Our preparations regarding the operation are ongoing. (Troop) transfers and preparations are still underway,” Akar said, according to state news agency Anadolu.

AFP journalists witnessed the arrival of a large convoy of vehicles in the Turkish town of Akcakale in Sanliurfa province overnight.

The Kurdish-led Syrian Democratic Forces said Turkish forces were shelling its positions over the border at Sere Kaniye.

The local Kurdish authority known as the Autonomous Administration of North and East Syria urged the international community to live up to its responsibilities as “a humanitarian catastrophe might befall our people” in the region.

“We call upon our people, of all ethnic groups, to move toward areas close to the border with Turkey to carry out acts of resistance during this sensitive historical time,” it said.

The statement said the mobilization would last for three days.

Meanwhile, ISIS jihadists targeted a post of the SDF in the northern Syrian city of Raqqa, which was once the de facto ISIS capital at the height of the militants’ power in the region.

The extremists launched three suicide bombings against Kurdish positions in Raqqa. There was no immediate word on casualties.

Trump cast his decision to pull back US troops from parts of northeast Syria as fulfilling a campaign promise to withdraw from the “endless war” in the Middle East.

Republican critics and others said he was sacrificing an American ally, the Syrian Kurds, and undermining US credibility around the globe.

With Post wires