The US National Security Council remains "fundamentally engaged" in a key South Korea-US nuclear deterrence dialogue platform, its top security official said Wednesday, as the two countries' defense authorities are now tasked with leading the body.

National Security Advisor Jake Sullivan made the remarks after senior defense officials from Seoul and Washington signed a framework document Monday to task Seoul's defense ministry and the Pentagon to lead the Nuclear Consultative Group.

During its inaugural and second sessions in July and December last year, respectively. the two countries' NSCs had led the NCG. The third meeting, slated to take place in June in Seoul, is to be led by the two defense authorities.

"The NSC remains fundamentally engaged in the NCG. And this is an interagency process. It involves our Department of Defense, the NSC, our intelligence community and the same on the other side," Sullivan said during a press briefing.

"The work of the NCG frankly speaks for itself and we will continue to be proud of that work because we believe it's enhancing security and extended deterrence in the US-ROK alliance," he added, referring to South Korea by its official name, the Republic of Korea.

He also touched on the Washington Declaration in which the establishment of the NCG was mentioned. President Yoon Suk Yeol and US President Joe Biden adopted the declaration during a summit last April as part of efforts to strengthen the credibility of America's extended deterrence commitment to using the full range of its military capabilities to defend its ally.

"The Washington Declaration, it remains a high priority for all of us," he said.

The NCG is a platform to discuss nuclear and strategic planning issues. At the last and second NCG session, the two sides agreed to complete the establishment of guidelines on the planning and operation of a shared nuclear strategy by the middle of this year. (Yonhap)