Washington: US President Donald Trump unveiled a revamped US missile defence strategy on Thursday that called North Korea an ongoing and "extraordinary threat," seven months after he declared the threat posed by Pyongyang had been eliminated.

A Hwasong-12 intermediate-range missile in Pyongyang, North Korea. Credit:AP

The plan, which also detailed concerns about the burgeoning capabilities of Iran, Russia and China, called for developing space-based sensors to detect incoming enemy missiles and exploring space-based weapons to shoot down missiles among other steps to shield the United States.

The open acknowledgment in the Missile Defence Review of US plans to counter Russian and Chinese technological advances likely will alarm those nations. It marked a departure from the approach taken by Republican Trump's Democratic predecessor, Barack Obama, to tamp down concerns by major nuclear powers about expanding US missile defences.

"Our goal is simple: To ensure we can detect and destroy any missile launched against the United States - anywhere, anytime, any place," Trump said at the Pentagon.