North Korea will launch its first military reconnaissance satellite in June for monitoring movements from the United States, Pyongyang's state-run news agency KCNA reported on Tuesday.
Ri Pyong Chol, vice-chairman of North Korea's Central Military Commission, said space-based monitoring was needed to fend off Washington's "reckless" military exercises with South Korea.
The statement came a day after North Korea told Japan's coast guard of its launch intentions and that it would occur sometime between May 31 and June 11, adding the maneuver might affect waters in the Yellow Sea, East China Sea and east of the Philippines' Luzon Island.
Japan says it will shoot down satellite
Tokyo's defense minister warned its forces to shoot down the satellite or debris, if any entered Japanese territory, while its coast guard issued a safety warning for vessels.
US and South Korean forces have carried out several joint missions in recent months, including the biggest-ever live-fire exercises earlier this month.
North Korea weighing up current, future 'threats'
Ri said the joint exercises meant Pyongyang had to respond with the "means capable of gathering information about the military acts of the enemy in real time."
"We will comprehensively consider the present and future threats and put into more thoroughgoing practice the activities for strengthening all-inclusive and practical war deterrents," Ri said in the statement carried by the KCNA news agency.