In recent days, US officials have said evidence such as photographs from spy satellites indicated that North Korea might be preparing to test launch a long-range missile.
Washington and others have warned Pyongyang that such a launch would pose a grave danger to regional security.
A USAF statement said that an improved U-2S Dragon Lady had arrived at Osan Air Base in South Korea on June 14.
The plane's cockpit offered more information to pilots than older U-2 planes as well as improved safety features, it said.
''The arrival is part of a previously planned deployment,'' a US Forces Korea official said. He gave no more details.
Seoul's Yonhap news agency said two more of the updated U-2 planes might be heading to South Korea to replace older planes.
The United States has long stationed U-2s at Osan, using them to keep a close eye on North Korea through extremely high altitude reconnaissance missions.
Pyongyang regularly complains about the flights. Last week it said the reconnaissance missions increased the chance of an aerial confrontation.
The Central Intelligence Agency commissioned and operated the plane and ran its missions until the US Air Force took over in 1974. Its first official flight was on August. 8, 1955.
The plane has been used to gather intelligence on every major conflict and period of tension involving the United States.
The U-2 uses a wide range of cutting-edge sensors to collect information ranging from air samples to aerial photographs for the US military and intelligence.
REUTERS SI PC1201