The U.S. military said it successfully tested a key missile defense system Friday, in a milestone that experts say shows a growing U.S. capability to knock down an incoming, medium-range missile from countries like North Korea and Iran.

The Aegis system used in the latest test was fitted with a Standard Missile 3 Block IIA (SM-3 IIA) interceptor being developed in a joint venture between Raytheon Co. and Mitsubishi Heavy Industries Ltd.

It was the second successful intercept in a row for the SM-3 IIA and will give the U.S. Missile Defense Agency more confidence that it has resolved design flaws that previously caused intercept failures, U.S. officials said, speaking on condition of anonymity.