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 fighters who were the reason U.S. forces came in the first place.

The Turks began attacks in Syria last week against Syrian Kurdish fighters, longtime U.S. battlefield allies against the IS group. On Monday, Syrian government troops moved north toward the border region, setting up a potential clash with Turkish-led forces.

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.

In Washington, Trump said in a statement that 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.

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 hurried preparations, triggered by Trump's decision Saturday to expand a limited troop pullout into a complete withdrawal, came as Trump's national security team considered imposing what he called "big sanctions" on NATO ally Turkey.

The U.S. pullout raised many questions, including how and whether the Trump administration would continue putting military pressure on the Islamic State in Syria without a troop presence on the ground. U.S. forces have been there since 2015, arming and advising a Kurdish-led Syrian group of fighters who largely eliminated IS control of Syrian territory but were still working to prevent an IS resurgence.

The defense official, who was not authorized to be quoted by name, said U.S. officials were weighing options for the future of a 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.

Defense Secretary Mark Esper said Sunday that Trump had directed U.S. troops in northern Syria to begin pulling out "as safely and quickly as possible." He did not say Trump ordered troops to leave Syria, but that seemed like the next step in a combat zone growing more unstable by the hour. The only exception, it appeared, is a group of perhaps 200 U.S. troops who will remain at a base in southern Syria near the Jordanian border, working with 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 wrote that the IS prisoners who escaped amid the pandemonium in Syria can be "easily recaptured" by Turkey or European nations, even as France said it was pulling its remaining troops out of Syria.

Trump 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.

It's not a new issue for the president. He rallied around it in 2016 and, during his term, has repeatedly urged bringing the troops home only to be talked out of it by moderating forces including former Defense Secretary James Mattis and chief of staff John Kelly. Mattis resigned last December when Trump announced -- and later partly rescinded -- a decision to pull all troops out of Syria.

In his remarks Sunday, Esper said the administration had little choice but to order a pullout.

"We have American forces likely caught between two opposing advancing armies and it's a very untenable situation," Esper said.

This seemed likely to herald the end of a five-year effort to partner with Syrian Kurdish and Arab fighters to ensure a lasting defeat of the Islamic State group. Hundreds of IS supporters escaped a holding camp amid clashes between invading Turkish-led forces and Kurdish fighters, and analysts said an IS resurgence seemed more likely, just months after Trump declared the extremists defeated.

Republican Senate leader Mitch McConnell, normally a staunch Trump supporter, said he was "gravely concerned" by events in Syria and Trump's response so far.

Withdrawing U.S. forces from Syria "would re-create the very conditions that we have worked hard to destroy and invite the resurgence of ISIS," he said in a statement. "And such a withdrawal would also create a broader power vacuum in Syria that will be exploited by Iran and Russia, a catastrophic outcome for the United States' strategic interests."

However, Trump got quick support from Republican Sen. Lindsey Graham of South Carolina, who had lambasted his withdrawal decision last week as "shortsighted," ''irresponsible" and "unnerving to its core." On Monday, echoing Trump, Graham said on Fox News Channel that the current situation was Turkish leader Recep Tayyip Erdogan's fault and Turkey would face "crippling sanctions" from the U.S. on its economy.

The U.S. has had about 1,000 troops in northeastern Syria allied with the Kurdish-led Syrian Democratic Forces to combat IS. The Pentagon previously had pulled about 30 of these troops from the Turkish attack zone along the border. With an escalation of violence, a widening of the Turkish incursion and the prospect of a deepening conflict, all U.S. forces along the border will now follow that move. It was unclear where they would go.

The Kurds have turned to the Syrian government and Russia for military assistance, further complicating the battlefield.

The prospect of enhancing the Syrian government's position on the battlefield and inviting Russia to get more directly involved is seen by Trump's critics as a major mistake. But he tweeted that it shouldn't matter.

"Others may want to come in and fight for one side or the other," he wrote. "Let them!"

New Jersey Sen. Bob Menendez, the top Democrat on the Senate Foreign Relations Committee, said Trump is weakening America. 'To be clear, this administration's chaotic and haphazard approach to policy by tweet is endangering the lives of U.S. troops and civilians," Menendez said in a statement. "The only beneficiaries of this action are ISIS, Iran and Russia."

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AP writer Jonathan Lemire contributed to this story.

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