North Korea poses major threats to "vital interests" of the United States as it continues to advance its missile and nuclear capabilities, a Washington-based think tank report showed Wednesday.

According to the "2021 Index of US Military Strength," an annual report published by the Heritage Foundation, North Korea was ranked as "high" in terms of threat level, the second highest out of its five-tier threat assessment scale. It came in the same category with Russia, Iran and China.

The North's threat level, however, was unchanged from a year earlier.

In terms of threat capability, North Korea was ranked as "gathering," a step shy of the top "formidable" level, the report showed. Iran was categorized in the same level with the North.

"US and allied intelligence agencies assess that Pyongyang has already achieved nuclear warhead miniaturization, the ability to place nuclear weapons on its medium-range missiles, and an ability to reach the continental United States with a missile," it added.

North Korea conducted a total of six nuclear weapons tests. It carried out three intercontinental ballistic missile tests in 2017, though it has maintained a self-imposed moratorium on nuclear and long-range missile tests amid now-stalled denuclearization talks with Washington.

The North showcased its largest-ever ICBM during a massive military parade held to mark the 75th founding anniversary of its ruling Workers' Party last month.

The report said the North has not yet conducted an ICBM test that successfully showed a reentry vehicle capability, but US intelligence authorities assessed that Pyongyang's ICBM reentry vehicles "would likely perform adequately if flown on a normal trajectory to continental US targets." (Yonhap)