US Defense Secretary Ash Carter said on Wednesday the US military was keeping a vigilant eye on North Korea's missile and nuclear programs, and was continually expanding its defenses against a possible missile attack by Pyongyang.
Carter said the United States was on track to expand the number of ground-based missile interceptors in Alaska and Hawaii to 44 from 30, and improve their quality, but no further interceptor expansion was planned for now.
Asked if Washington was looking to add more interceptors to those already planned, Carter told reporters: "At the moment, no. That calculus stands... The plan has not changed."
North Korea told UN agencies on Tuesday it plans to launch a satellite as early as next week, a move that could advance the country's long-range missile technology after its fourth nuclear test on Jan. 6.
News of the planned launch drew fresh US calls for tougher U.N. sanctions already under discussion in response to North Korea's nuclear test last month.
Carter said the United States remained concerned about North Korea's development of intercontinental ballistic missiles and nuclear weapons, and was investing heavily to continue to improve US defenses against a possible attack.
The defense secretary spoke with reporters after a visit to Marine Corps Air Station Miramar in California, where he vowed to increase funding for servicing aging aircraft and accelerate purchases of new planes to ensure higher readiness rates.