The Pentagon scored an important success today in a test of its oft-criticised missile defence programme, destroying a mock warhead over the Pacific Ocean with an interceptor that is key to protecting US territory from a North Korean attack.
Vice Admiral Jim Syring, director of the Pentagon agency in charge of developing the missile defence system, called the test result "an incredible accomplishment" and a critical milestone for a programme hampered by setbacks over the years.
"This system is vitally important to the defence of our homeland, and this test demonstrates that we have a capable, credible deterrent against a very real threat," Syring said in a written statement announcing the test result.
Despite the success, the US$244m test didn't confirm that under wartime conditions the US could intercept an intercontinental-range missile fired by North Korea.
Pyongyang is understood to be moving closer to the capability of putting a nuclear warhead on such an ICBM and could develop decoys sophisticated enough to trick an interceptor into missing the real warhead.
Syring's agency sounded a note of caution.
"Initial indications are that the test met its primary objective, but programme officials will continue to evaluate system performance based upon telemetry and other data obtained during the test," his statement said.
The most recent intercept test, in June 2014, was successful, but the longer track record is spotty.
Since the system was declared ready for potential combat use in 2004, only four of nine intercept attempts have been successful.
The Pentagon is still incorporating engineering upgrades to its missile interceptor, which has yet to be fully tested in realistic conditions.
North Korea says its nuclear and missile programmes are a defence against perceived US military threats.
Its accelerating missile development has complicated Pentagon calculations, most recently by incorporating solid-fuel technology into its rockets.
The step would mean even less launch warning time for the United States.
Liquid fuel is less stable and rockets using it have to be fuelled in the field, a process that takes longer and can be detected by satellites.
Underscoring its uninterrupted efforts, North Korea on Monday fired a short-range ballistic missile that landed in Japan's maritime economic zone.