US National Security Advisor Jake Sullivan highlighted "synergies" in trilateral cooperation between South Korea, the United States and Japan in security, technology and other fields on Tuesday, the eve of a summit between President Joe Biden and Japanese Prime Minister Fumio Kishida.

Sullivan made the remarks as he previewed the White House summit on what he called issues "across the board," including defense, space cooperation and research partnerships on critical technologies, including artificial intelligence and semiconductors.

"I believe I don't necessarily like to use the word synergies very often, but I do believe that there are synergies on a trilateral basis in terms of our technological, industrial, economic capacity, as well as our security and military cooperation," Sullivan told a press briefing.

"We want to build on that. For tomorrow, what we are announcing will be bilateral measures in this space. And then of course, we will be open in the future to discussing things more (on trilateral cooperation)," he added.

He was responding to a question about the future of defense industry cooperation among South Korea, the US and Japan amid speculation that Biden and Kishida will announce bilateral collaboration on joint development and production of military equipment.

Asked about the US position on Japan's diplomatic outreach to Pyongyang, Sullivan underscored the importance of "principled diplomacy."

"Speaking from the US perspective, we believe that principled diplomacy is a good thing. It's a necessary component of an overall strategy to confront the North Korean threat," he said. "We ourselves have indicated we are prepared to engage in diplomacy with North Korea. Of course the North Koreans have not shown any interest in that.

He went on to highlight that Pyongyang has only tried to "move down the track of further development of their missile and nuclear programs."

"So, we, the United States, have pulled closer together with our allies to enhance our capacity and posture in the Indo-Pacific, and we will continue to do that," he said. (Yonhap)