"I have been concerned for some time that North Korea would conduct what would be its seventh nuclear test going back multiple administrations. And I remain concerned about that," National Security Advisor Jake Sullivan told CBS talk show "Face the Nation" in an interview.

"I don't see any immediate indications that that's going to happen," he added.

"But it would not come as a surprise if North Korea moved forward with another nuclear test with respect to its intercontinental ballistic missile capability."

Sullivan stressed that Pyongyang had begun testing its nuclear capacity several years ago and "they have continued to test it."

North Korea said Thursday it successfully test-fired the reclusive country's newest ICBM, with leader Kim Jong Un personally overseeing the launch.

The missile, a solid-fuel Hwasong-18 that had reportedly been test-fired only once before, flew 1,001 kilometres (622 miles) at a maximum altitude of 6,648 kilometres before splashing into the East Sea, also known as the Sea of Japan, the official Korean Central News Agency reported.

Relations between North and South Korea are at a low point. Last year, Kim declared his country an "irreversible" nuclear power, and has called for ramped-up weapons production, including of tactical nukes.

The United Nations, the United States and its allies including France strongly condemned Wednesday's launch, which violated multiple UN Security Council resolutions.

Sullivan nevertheless reiterated Washington's offer of negotiations with Pyongyang, saying President Joe Biden's administration is "prepared to sit down and talk without preconditions about their nuclear program."