WASHINGTON (Reuters) – The Pentagon on Thursday said it has 2,000 U.S. troops in Syria, more than twice the 900 it has previously said it has, and that the additional troops are considered temporary forces that were sent to support the mission against Islamic State militants.

Pentagon spokesperson Major General Pat Ryder told reporters he did not know how long the number had been 2,000, but it was probably months at a minimum and pre-dated the fall of Syrian leader Bashar al-Assad.

“I learned the number today … as somebody who’s been standing up here telling you 900, I wanted to get you what we had on that,” Ryder said.

The United States had said publicly for several years that it had 900 troops in Syria who were working with local forces to prevent a resurgence of Islamic State, which in 2014 seized large swathes of Iraq and Syria but was later pushed back.

President Joe Biden’s administration has said that U.S. troops will be staying in Syria, though President-elect Donald Trump could remove them when he takes office on Jan. 20.

(Reporting by Idrees Ali and Phil Stewart, editing by Deepa Babington)