Washington, DC - The Pentagon has revealed that the true number of US troops in Syria is around 2,000, more than double the number that had been previously disclosed by the US government.

US troops stationed in Syria to combat the Islamic State had previously been thought to number around 900.

Pentagon press secretary Pat Ryder said this was an error, as it only accounted for the number of troops stationed in Syria on a long-term basis of around nine-to-12 months.

According to Ryder, the troops have been there since well before the fall of the Assad regime and will likely stay to continue their "Defeat ISIS Mission."

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"As I understand it, and as it was explained to me, these additional forces are considered temporary rotational forces that deploy to meet shifting mission requirements, whereas the core 900 deployers are on longer term deployments."

The news comes as a US delegation arrived in Syria for meetings with representatives of the Hayat Tahrir al-Sham (HTS) de facto government in Damascus.

Countering ISIS and continued US troop presence in Syria will likely be on the cards for the delegation, as well as the country's transition after Bashar al-Assad was ousted less than two weeks ago.

In a press briefing on Thursday, State Department spokesperson Vedant Patel outlined what Washington wants to see out of the new HTS government.

"It needs to be inclusive, it needs to protect the rights of all Syrians including women and minorities," Patel explained. "Like all governments, it needs to preserve critical state institutions and deliver essential services."

"And perhaps most important, we want to see a Syria that does not pose a threat to its neighbors or the regions or Syrians – or Syria being a place that's going to serve as a base for terrorism or allying with groups like ISIS."

The US has imposed crippling sanctions on Syria for years, while its main client state in the region, Israel, has illegally invaded Syrian territory since Assad's fall.