WASHINGTON (AP) — Targeting Turkey’s economy, President Donald Trump announced sanctions Monday aimed at restraining the Turks’ assault against Kurdish fighters and civilians in Syria — an assault Turkey began after Trump announced he was moving U.S. troops out of the way.

Meanwhile, the Americans were scrambling for Syria’s exits, a move criticized at home and abroad as opening the door to a resurgence of the Islamic State group whose violent takeover of Syrian and Iraq lands five years ago was the reason American forces came in the first place.

Trump said the approximately 1,000 U.S. troops who had been partnering with local Kurdish fighters to battle IS in northern Syria are leaving the country. They will remain in the Middle East, he said, to “monitor the situation” and to prevent a revival of IS — a goal that even Trump’s allies say has become much harder as a result of the U.S. pullout.

The Turks began attacks in Syria last week against the Syrian Kurdish fighters, whom the Turks see as terrorists. On Monday, Syrian government troops moved north toward the border region, setting up a potential clash with Turkish-led forces.

Trump said Turkey’s invasion is “precipitating a humanitarian crisis and setting conditions for possible war crimes,” a reference to reports of Turkish-backed fighters executing Kurdish fighters on the battlefield.

The Kurdish forces previously allied with the U.S. said they had reached a deal with President Bashar Assad’s government to help them fend off Turkey’s invasion, a move that brings Russian forces deeper into the conflict.

In his sanctions announcement, Trump said he was halting trade negotiations with Turkey and raising steel tariffs. He said he would soon sign an order permitting sanctions to be imposed on current and former Turkish officials.

“I am fully prepared to swiftly destroy Turkey’s economy if Turkish leaders continue down this dangerous and destructive path,” Trump said.

American troops consolidated their positions in northern Syria on Monday and prepared to evacuate equipment in advance of a full withdrawal , a U.S. defense official said.

The official, who was not authorized to be quoted by name, said U.S. officials were weighing options for a potential future counter-IS campaign, including the possibility of waging it with a combination of air power and special operations forces based outside of Syria, perhaps in Iraq.

The hurried preparations for a U.S. exit were triggered by Trump’s decision Saturday to expand a limited troop pullout into a complete withdrawal.

Defense Secretary Mark Esper said Monday he would travel to NATO headquarters in Brussels next week to urge European allies to impose “diplomatic and economic measures” against Turkey — a fellow NATO ally — for what Esper called Ankara’s “egregious” actions.

Esper said Turkey’s incursion had created unacceptable risk to U.S. forces in northern Syria and “we also are at risk of being engulfed in a broader conflict.”

The only exception to the U.S. withdrawal from Syria is a group of perhaps 200 troops who will remain at a base called Tanf in southern Syria near the Jordanian border along the strategically important Baghdad-to-Damascus highway. Those troops work with Syrian opposition forces unrelated to the Kurdish-led fighters in northern Syria.

Esper said the U.S. withdrawal would be done carefully to protect the troops and to ensure that no U.S. equipment was left behind. He declined to say how long that might take.

In a series of tweets Monday, Trump defended his gamble that pulling U.S. forces out of Syria would not weaken U.S. security and credibility. He took sarcastic swipes at critics who say his Syria withdrawal amounts to a betrayal of the Kurds and plays into the hands of Russia.

“Anyone who wants to assist Syria in protecting the Kurds is good with me, whether it is Russia, China, or Napoleon Bonaparte,” he wrote. “I hope they all do great, we are 7,000 miles away!”

Trump has dug in on his decision to pull out the troops, believing it fulfills a key campaign promise and will be a winning issue in the 2020 election, according to White House officials.