Trump orders US troops to leave Syria as White House declares victory over ISIS originally appeared on abcnews.go.com

The Pentagon announced Wednesday that it has started the process of withdrawing all 2,000 U.S. troops from Syria after the White House confirmed President Donald Trump had given the surprise order to leave because ISIS there had been "defeated."

The announcement was met with backlash from Capitol Hill, especially from Republican senators, and Wednesday afternoon Senate Foreign Relations Committee Chairman Bob Corker, R-Tenn., was headed to the White House for an unscheduled meeting with the president.

President Trump's decision followed a phone call with Turkey's President Recep Tayyip Erdogan last Friday which triggered the decision, a U.S. official told ABC News. During that call, Trump told Erdogan that he was planning to pull U.S. troops out of Syria, a senior Turkish official said.

“Five years ago, ISIS was a very powerful and dangerous force in the Middle East, and now the United States has defeated the territorial caliphate," White House press secretary Sarah Sanders said in a statement. "These victories over ISIS in Syria do not signal the end of the Global Coalition or its campaign.”

Earlier Wednesday, amid breaking news reports about the withdrawal, Trump tweeted that ISIS has been "defeated" in Syria, saying it was "my only reason for being there during the Trump Presidency."

We have defeated ISIS in Syria, my only reason for being there during the Trump Presidency. — Donald J. Trump (@realDonaldTrump) December 19, 2018

Chief Pentagon spokesperson Dana White said in a statement on Wednesday that the U.S. had "started the process of returning U.S. troops home from Syria." Once officially ordered by Defense Secretary James Mattis, the withdrawal would be completed within 30 days, an official told ABC News.

(MORE: President Trump's troop withdrawal from Syria a 'huge' mistake: Senator Lindsey Graham)

A second U.S. official said the withdrawal would be dependent on the security environment for the American units, so that it's safe for them to leave. Mattis has not yet signed the orders that would trigger the actual withdrawal, those officials said, though they have been drafted by the Joint Staff.

The State Department is already beginning to pull out the dozen U.S. diplomats from Syria who were running programs to stabilize areas liberated from ISIS, a third U.S. official told ABC News.

PHOTO: President Recep Tayyip Erdogan speaks about the murder of Saudi journalist Jamal Khashoggi during his weekly parliamentary address, Oct. 23, 2018, in Ankara, Turkey. (Getty Images) More

Trump's call with Erdogan on Friday followed a week of rising tension with Ankara, including the Turkish leader saying he would launch a military operation against U.S.-backed Kurdish fighters in northeast Syria "within a few days."

The third official told ABC News that the call made it clear that Trump never bought into the idea of keeping U.S. troops in Syria, despite officials believing they had convinced him otherwise.

While Erdogan and other world leaders such as Israel's Benjamin Netanyahu were alerted to the president's impending decision earlier, some top U.S. officials were unaware until Tuesday.

Later on Wednesday, the State Department also announced an intended $3.5 billion sale of the U.S. Patriot missile system to Turkey.

There are about 2,000 U.S. troops in eastern Syria advising and assisting the Kurdish-led Syrian Democratic Forces (SDF) in the fight against ISIS. The first U.S. troops arrived in Syria under the Obama administration in October 2015. The original force of 50 U.S. advisers grew to an official level of more than 500, though it actually grew beyond that figure to approximately 2,000 over the following year.

PHOTO: U.S. Army Maj. Gen. Jamie Jarrard (L), thanks Manbij Military Council commander Muhammed Abu Adeel during a visit to a small outpost near the town of Manbij, northern Syria, Feb. 7, 2018. (Susannah George/AP) More

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