The US military is redeploying its troops from an American-led coalition base in Iraq to Afghanistan following the defeat of Deash in the country, Fox News reported.
The report said that it western contractors at the base say US troops began the drawdown over the past week, with groups of soldiers leaving the base on daily flights.
However, the exact scale of the redeployment was unclear.
According to various estimates, as of 2016, there were more 5,000 US military personnel stationed in Iraq, with nearly 4,000 deployed to support and assist local groups fighting Daesh militants.
The remaining personnel included special operations forces, logistical workers and troops on temporary rotations, the BBC reported.
Iraqi officials reportedly said their government reached an agreement with the US-led coalition to reduce the number of troops in Iraq.
The reported military buildup in Afghanistan is the latest sign of a growing US focus on Afghanistan as the primary conflict.
The White House reportedly signed off in August on deploying an additional 4,000 troops in Afghanistan.
The US Army is also floating plans to increase the total US force in the country by 1,000 in a bid to boost Afghan forces' fight against the Taliban, the Washington Post reported.
Since Trump took office, the number of troops has nearly doubled in Afghanistan - from 8,500 in early 2017 to 14,000 today.