JUST IN: Biden’s Pentagon reveals there are 2,000 US troops in Syria—not 900 as they previously thought

Ryder told reporters, "As you know, we have been briefing you regularly that there are approximately 900 US troops deployed to Syria. In light of the situation in Syria and the significant interest, we recently learned that those numbers were higher, and so asked to look into it. I learned today that in fact there are approximately 2,000 US troops in Syria."

Ryder said that as he understood, those included in that 900 figure are on longer-term deployments, while the additional forces "are considered temporary rotational forces that deploy to meet shifting mission requirements."

"And as you know, for many of our deployments, numbers will fluctuate from time to time. But given that this number is significantly higher than what we've been briefing, I wanted to let you know as soon as I found out this information," Ryder added.

He later explained when asked about it by a reporter that the longer-term forces are there for nine to 12 months, while those temporary forces are "going to rotate in on a 30 to 90-day basis." He said that these additional troops were likely in place before the fall of the Assad regime.

In early December, Syrian leader Bashar al-Assad fled his country after Damascus was stormed by rebels, ending the six-decade rule of the Assad family in the country. Following this, the US Central Command and Israel conducted dozens of airstrikes on targets in central Syria attempting to wipe out ISIS strongholds.

US officials have warned that thousands of ISIS fighters currently imprisoned in Syria may attempt a jailbreak. The US-backed Kurdish-Syrian Democratic Forces (SDF) is currently holding 9,000 ISIS soldiers and 50,000 others in detention centers that are inadequately secured.