WASHINGTON – Declaring victory over the Islamic State, President Donald Trump has ordered U.S troops in Syria be withdrawn from their posts, the White House said Wednesday.

The withdrawal of the more than 2,000 troops is based on Trump’s decision that the mission against ISIS is complete, a U.S. official, who was not authorized to speak publicly before it was announced by the White House, told USA TODAY.

White House press secretary Sarah Sanders said Wednesday that the U.S. has “defeated the territorial caliphate.”

“These victories over ISIS in Syria do not signal the end of the Global Coalition or its campaign,” Sanders said in a statement. “We have started returning United States troops home as we transition to the next phase of this campaign.”

She did not offer details on the “next phase” of the campaign against ISIS in her statement.

In a tweet earlier on Wednesday morning, Trump also declared victory.

“We have defeated ISIS in Syria, my only reason for being there during the Trump Presidency,” he wrote.

Despite Trump’s claims that the war against the Islamic State has been won, fighting by U.S.-led forces continues there.

On Saturday, there were 47 airstrikes conducted by war planes against ISIS targets, U.S. Central Command announced early Wednesday. The bombs struck 20 ISIS fighting units, destroyed petroleum tanks, a tunnel, vehicle and a mortar-firing position.

Further, according to a recent report by the Center for Strategic and International Studies, ISIS is far from obliterated. The Washington-based think tank estimates ISIS may still possess between 20,000 to 30,000 militants in Iraq and Syria.

As recently as last week, officials said U.S. troops may need a longer stay to ensure that the military’s accomplishments are “enduring.”

“I think it’s fair to say Americans will remain on the ground after the physical defeat of the caliphate, until we have the pieces in place to ensure that that defeat is enduring,” said Brett McGurk, Special Presidential Envoy for the Global Coalition to Defeat ISIS.

Marine Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff, declined earlier in December to put a timeline on withdrawal of U.S. troops from Syria, suggesting they would be needed for some time to establish conditions for a long-term peace agreement.

“We still have a long way to go and so I’d be reluctant to give a fixed time,” Dunford said during a forum held by the Washington Post.

The U.S.-led coalition has been fighting ISIS in the countries since 2014.

More: Syria conflict explained: How did we end up here?

U.S. troops, mostly special operations units, have been training local security forces in eastern Syria.

In September, Defense Secretary Jim Mattis told reporters the U.S. forces also helped deter Iran from increasing its influence in the region. The U.S. goal has been to beat back ISIS enough to allow the United Nations to broker a peace plan to end years of fighting that have killed hundreds of thousands of civilians and created a humanitarian and refugee crisis.

“We want to support the Geneva process, the U.N.-mandated process,” Mattis said in September. “In that scope what we want to do is make certain that ISIS does not come back and upset everything again.”

Contributing: Kim Hjelmgaard and David Jackson