WASHINGTON (Reuters) - The United States is poised to move about 1,000 U.S. troops from northern Syria amid an ongoing Turkish incursion into the region, Defense Secretary Mark Esper said on Sunday, calling the situation “untenable” for U.S. forces.

The pull-back of troops from the region dovetails with President Donald Trump’s long-standing desire for the United States to extract itself from foreign conflicts. It comes after Trump a week ago withdrew some U.S. troops deployed to support Kurdish forces in the fight against Islamic State.

That decision, which came under heavy fire from fellow Republicans and allies, helped open the door for Turkey to launch an offensive against the U.S.-backed Kurdish forces, part of the Syrian Democratic Forces (SDF), who have been America’s most capable partners in quashing Islamic State.

“In the last 24 hours, we learned that [the Turks] likely intend to extend their attack further south than originally planned, and to the west,” Esper said on CBS’ “Face the Nation.”

“We also have learned in the last 24 hours that the ... SDF are looking to cut a deal, if you will, with the Syrians and the Russians to counterattack against the Turks in the north.”

Esper said he spoke with Trump Saturday night, and that the president directed the U.S. military to “begin a deliberate withdrawal of forces from northern Syria.”

U.S. officials had spent the last week ramping up pressure on Turkey to halt the assault on Syria and the Kurdish fighters that it considers a threat to national security.

U.S. Treasury Secretary Steven Mnuchin on Friday said sanctions against Ankara were all ready should the president choose to make good on his threat to obliterate Turkey’s economy.

Turkey’s offensive has raised alarm bells around the world amid concerns about its impact on civilians and the possibility of Islamic State militants escaping from Kurdish-led authorities.

U.S. President Donald Trump pauses as he addresses conservative activists at the Family Research Council's annual gala in Washington, U.S., October 12, 2019. REUTERS/Yuri Gripas

Esper said the United States knew ahead of time about Turkish President Recep Tayyip Erdogan’s intentions to cross the border into Syria.

“It was clear to me that President Erdogan was committed to coming in. He informed us that he was coming in. He didn’t ask permission.”

He added that the United States simply did not have enough troops to stop a Turkish advance and they needed to be taken out of harm’s way.

“There is no way they could stop 15,000 Turks from proceeding south,” he said.

TROOP MOVEMENTS

Esper did not put a timeline on how long the drawdown from northern Syria would take or whether the troops would be relocated within Syria or moved out of the country entirely.

One official suggested that the troops would be moving away from northern Syria, but still saying in Syria.

Another U.S. official, speaking on the condition of anonymity, said it was difficult to imagine troops staying without having a presence in northern Syria, which is the primary route through which American supplies move. But the official added that the situation was fluid.

It is also not clear what will happen with the several hundred troops that are located at the U.S. military outpost of Tanf, near the border with Iraq and Jordan.

The Tanf garrison was set up when Islamic State fighters controlled eastern Syria bordering Iraq. But since the militants were driven out, Tanf has assumed a role as part of a U.S. strategy to contain Iran’s military buildup.

“Very smart not to be involved in the intense fighting along the Turkish Border, for a change,” Trump said on Twitter on Sunday.

“Those that mistakenly got us into the Middle East Wars are still pushing to fight. They have no idea what a bad decision they have made. Why are they not asking for a Declaration of War?,” he added.

Over the past few days, U.S. military officials have become increasingly concerned about the safety of American troops.

On Friday, the Pentagon said U.S. troops in northern Syria came under artillery fire from Turkish positions, even though Ankara knew that American troops were located there.

Two U.S. officials told Reuters on Sunday that a small number of U.S. troops have left an outpost in the town of Ain Issa in northern Syria because of concerns about a Turkish incursion that is pushing into Syria.

The decision to move U.S. troops out of northern Syria will intensify concerns that the Turkish incursion could allow Islamic State to resurge.

Those fears were highlighted on Sunday, when the Kurdish-led administration in northern Syria said 785 foreigners affiliated with Islamic State managed to escape a camp where they were being held following Turkish shelling.

Former U.S. Defense Secretary Jim Mattis said on Sunday that the United States needed to keep the pressure on the militant group.

“If we don’t keep the pressure on, then ISIS will resurge,” Mattis said NBC’s “Meet the Press.” He was using an acronym for Islamic State.