Iraq's al-Maalomah news agency cited an informed source on Saturday as saying that US troops have started working on "broadening the area of the base" and further developing structures accommodating US troops, Press TV reported.
According to the report, US forces are also setting up barbed wire and "various defensive structures" along with signs warning against approaching the base.
The source added that Iraqi forces inside the airbase are unaware of the American measures because details regarding the movements are limited to the jurisdiction of the Office of the Commander-in-Chief of Iraq's Armed Forces.
The report comes nearly a month after the base was the target of a major Iranian missile attack in response to the assassination of senior Iranian commander Lieutenant General Qassem Soleimani on January 3.
The Trump administration initially claimed that little material damage had been done and no Americans had been injured in the strikes.
Washington has since gradually confirmed casualties from the Iranian attack, most recently claiming that 64 US troops were injured as a result of the strikes.
The reported American defensive measures also come as Iraqi resistance groups and influential figures have vowed to mobilize against American presence in the country if Washington does not withdraw troops from Iraq.
On January 5, the Iraqi parliament voted to expel US forces from the country in response to the assassination of General Soleimani and Abu Mahdi al-Muhandis who accompanied him and was second-in-command of Iraq's Popular Mobilization Units (PMU).