(CNN) The US military has moved additional troops into Syria in recent days to help provide protection to other US service members as they withdraw under President Donald Trump's directive to pullout all US troops from the country, according to two US defense officials. The officials would not reveal where in the country the troops are or how many have been sent.

Defense officials have acknowledged that a security force of armed troops -- possibly infantry -- would be needed to help carry out the withdrawal of US forces over time. The additional troops that have moved in are needed to provide security for troops and equipment as they are moved out by land and air as well a provide additional security on the ground as the number of US forces dwindles, officials said.

The officials said the additional security forces may move around Syria to different locations as needed and may move in and out of the country at times.

They would not indicate if any troop withdrawals have taken place or will happen in the immediate future, citing security concerns .

The number of US troops routinely deployed in Syria to fight ISIS, and assist local forces, has hovered between 2,000 and 2,500 in recent months at locations in northern, eastern and southern Syria. All of the current missions are continuing the official said. But with the new personnel moving in and out of Syria, and existing forces expected to withdraw, the overall number will now fluctuate.

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