The U.S. has confirmed that it continues to conduct interceptor missile tests to prepare against possible long range missile attacks from North Korea, targeting U.S. mainland.

Director of the U.S. Missile Defense Agency Patrick O'Reilly made the remark at a House Armed Services Committee hearing Thursday. He said a version of a ground-based midcourse defense (GMD) missile has performed well noting that all three intercept attempts were successful.

He said warheads fired from Alaska have been taken down by interceptors launched in California and this roughly equates to the geometry of a launch out of North Korea.

Speaking at the hearing, deputy assistant secretary of defense Bradley Roberts expressed concern that North Korea and Iran continue to develop long range missiles that threaten the U.S.