The US Air Force started positioning unmanned reconnaissance aircraft at an air base in Japan earlier this month as part of a rotational deployment, the armed service has said.

The RQ-4 Global Hawks began arriving at Yokota Air Base in Japan from Andersen Air Force Base in Guam last Monday, the US Pacific Air Forces said in a release Thursday.

The rotational deployment came at a time when North Korea has completed preparations to launch its first military spy satellite. Last week, the North's leader Kim Jong-un inspected the satellite, which is "ready for loading" on a rocket, according to the North's state media.

"The Global Hawk's mission is to provide a broad range of US intelligence, surveillance, and reconnaissance capabilities to support joint forces, and allies and partners in worldwide peacetime, contingency, and crisis operations," it said.

The unmanned aircraft has been rotationally operating from Yokota Air Base since 2017, it said. (Yonhap)