The measures include stepped-up electronic monitoring, deployment of missile interceptor ships, and activation of radar networks to areas near the Korean peninsula and western Pacific.

Three interceptor ships near Japan and the Philippines, as well as U.S.-based interceptors, are ready to shoot down the North Korean missile if space-, land-, and sea-based sensors determine its flight path is targeted at the United States or U.S. allies, said officials who spoke on condition of anonymity.

The Obama administration will regard any launch by North Korea as a violation of U.N. Security Council resolutions regardless of whether the North Koreans claim the rocket test is for space launch purposes, the officials said. The technology and rocketry used for a space launch is nearly identical to that used with ballistic missiles that carry a warhead, they said.