Feb. 16 (UPI) -- A U.S. spy plane and a missile-tracking ship reportedly conducted surveillance missions over waters between the Korean Peninsula and northeast China, as the United States remains on guard for North Korea provocations.
South Korean military sources told News 1 on Tuesday that the plane, a U.S. RC-135S Cobra Ball, flew over the West Sea, also known as the Yellow Sea, on Feb. 3 ahead of the Lunar New Year.
The Cobra Ball previously has been deployed from Kadena Air Base in Okinawa, Japan. Online flights trackers in September showed the plane flying over the Yellow Sea, close to northern Chinese territory.
The U.S. Navy deployed the USNS Howard O. Lorenzen to the West Sea from Thursday to Sunday. The ship is equipped with X-band and S-band radar systems that can monitor and track regional ballistic missile launches.
The Howard O. Lorenzen, operational since 2014, was also deployed to waters near North Korea in 2016 and 2017, according to South Korean newspaper JoongAng Ilbo on Tuesday. North Korea conducted nuclear tests and launched an intercontinental ballistic missile at the time.
The ship's deployment came after South Korean military authorities told local media movements in North Korea indicated preparations for a large-scale artillery exercise along the country's eastern coast.
The U.S. ship's deployment off the western coast of the peninsula could be a sign the Navy is monitoring China, as well as Pyongyang, South Korean analysts said.
North Korea's Sohae Satellite Launching Station also could be the target of surveillance. Satellite images taken Jan. 30 showed snow removal at the facility where North Korea previously launched rockets for "peaceful purposes."
U.S. analysts Peter Makowsky and Jack Liu recently said on 38 North the removal ensures "consistent access to the principal facilities."
The United States and South Korea are expected to hold annual spring exercises in March. The exercises were postponed in 2020, according to Yonhap.