WASHINGTON (Associated Press)— The White House said Sunday that U.S. forces in northeast Syria will move aside and clear the way for an expected Turkish assault, essentially abandoning Kurdish fighters who fought alongside American forces in the yearslong battle to defeat Islamic State militants.

Turkish President Recep Tayyip Erdogan has threatened for months to launch the military operation across the border. He views the Kurdish forces as a threat to his country. Republicans and Democrats have warned that allowing the Turkish attack could lead to a massacre of the Kurds and send a troubling message to American allies across the globe.

U.S. troops “will not support or be involved in the operation” and “will no longer be in the immediate area,” in northern Syria, White House press secretary Stephanie Grisham said in an unusual late-Sunday statement that was silent on the fate of the Kurds. There are about 1,000 U.S. troops in northern Syria, and a senior U.S. official said they will pull back from the area — and potentially depart the country entirely should widespread fighting break out between Turkish and Kurdish forces.

The announcement followed a call between President Donald Trump and Erdogan, the White House said.

The decision is a stark illustration of Trump’s focus on ending American overseas entanglements — one of his key campaign promises. But his goal of swift withdrawals in Syria, Iraq and Afghanistan have been stymied by concerns from U.S. officials and American allies about the dangerous voids that would remain. As he faces an impeachment inquiry at home, Trump has appeared more focused on making good on his political pledges, even at the risk of sending a troubling signal to American allies abroad.

Key Republican leaders in Congress appeared taken aback by the move.

House Minority Leader Kevin McCarthy, R-Calif., said Monday in an appearance on “Fox & Friends” that he had not spoken with Trump about the decision and had concerns.

“I want to make sure we keep our word for those who fight with us and help us,” he said, adding that, “If you make a commitment and somebody is fighting with you. America should keep their word.”

One of the show’s hosts, Brian Kilmeade, asked McCarthy to try to intervene and “call the president before it’s too late.”

Sen. Lindsey Graham, R-S.C., one of Trump’s most vocal backers, also weighed in via tweet, saying that, “If press reports are accurate this is a disaster in the making.”

Trump, meanwhile, tweeted a lengthy defense Monday morning, writing in all-caps that, “WE WILL FIGHT WHERE IT IS TO OUR BENEFIT, AND ONLY FIGHT TO WIN.”

In December, Trump announced he was withdrawing American troops from Syria but was met with widespread condemnation for abandoning Kurdish allies to the Turkish assault. The announcement prompted the resignation in protest of then-Defense Secretary Jim Mattis, and a coordinated effort by then-national security adviser John Bolton to try to protect the Kurds.

Since January, U.S. officials have tried to broker the creation of a “safe zone” in northern Syria to provide a security buffer between the Turkish military and Kurdish forces, but Turkey has repeatedly objected to its slow implementation.

The White House announcement Sunday came a day after Erdogan offered the strongest warning yet of a unilateral military operation into northeastern Syria, as the Turkish military has been dispatching units and defense equipment to its border with the area.