North Korea can "range the continental United States" with an intercontinental ballistic missile and it would be prudent to assume Pyongyang can also miniaturize a nuclear warhead to put on an ICBM, the U.S. northern commander said Thursday.

"I assess that they have the ability to put an ICBM in space and range the continental United States and Canada," U.S. Northern Command Commander Adm. William Gortney said during a Senate Armed Services Committee hearing.

Asked if the range will then clearly include Hawaii and Alaska, the commander said, "Absolutely."

On the North's nuclear missile capabilities, Gortney said, "It's the prudent decision on my part to assume that he has the capability to ... miniaturize a nuclear weapon and put it on an ICBM" and "range all of the states of the United States and Canada."

Gortney stressed that the U.S. has the ability to defend against the North Korean threat.

"We have the ability to engage that threat," he said. "The intel community gives it a very low probability at success. But I don't think that American people want to base my readiness assessment on a low probability."

North Korea conducted its fourth nuclear test in January and a long-rocket launch in February, demonstrating to the outside world that it has made strides in efforts to develop a long-range missile capable of reaching the U.S.

Earlier this week, the North released photos of what it claims was a miniaturized nuclear warhead, with leader Kim Jong-un claiming that the country succeeded in making nuclear bombs small enough to fit on ballistic missiles.

South Korea's Defense Ministry said it believes the North has not yet mastered the nuclear warhead miniaturization technology. The U.S. Defense Department also said that the communist nation has not demonstrated those capabilities.

Adm. Cecil Haney, commander of U.S. Strategic Command, said he takes North Korean threats seriously.

"The nuclear test, the fourth test they just did here, and the space launch that they just did, further enhance their understanding and knowledge associated with this. North Korea has made many claims, miniaturization of nuclear warheads. They paraded around their KN-08 intercontinental ballistic missile," he told the hearing.

"I think we have take these problems seriously because it's clear to me they're working hard," he said. (Yonhap)