South Korea shares many common interests with the United States in the Indo-Pacific, including the nuclear challenge from North Korea and preserving freedom of navigation, a State Department spokesman said Tuesday.

"We share any number of interests, including the challenge of North Korea that we've talked about, including a free and open Indo-Pacific. And we've underlined and underscored our commitment to the region," Ned Price told a daily press briefing when asked about South Korea's possible consideration to join the US-led regional forum known as the Quad.

His remarks came as US President Joe Biden is set to hold a summit with his Quad counterparts.

The White House earlier said Biden will be joined by prime ministers Scott Morrison of Australia, Narendra Modi of India and Yoshihide Suga of Japan on Friday for the first-ever Quad summit.

Seoul has been reluctant to join the regional forum, which the former Trump administration had promoted as its major tool to counter what it had called Chinese aggression.

However, a member of South Korea's presidential policy planning commission said this week that Seoul's Moon Jae-in government was considering joining an expanded Quad.

"The Moon government is even pondering whether to join a potential Quad+ to show its commitment to the US-ROK alliance and, indirectly, influence Biden's North Korea policy," Hwang Ji-whan wrote in an op-ed co-authored by Ramon Pacheco Pardo, associate professor in international relations at King's College in London, and published by US daily The Hill.

ROK stands for South Korea's official name, the Republic of Korea.

Price said he will not make any projections about Seoul's participation in the Quad, but noted his country will continue to engage with South Korea multilaterally, as well as bilaterally.

"So I think you will see, just as you did in the first trilateral meeting between the acting assistant secretary and our South Korean and Japanese allies, that we will engage with the South Koreans bilaterally. We will engage with them multilaterally. We will engage with them as the treaty ally that they are, an important friend to the United States that they are," said the spokesman.

Price also underscored the importance of cooperation between his country and South Korea and other US allies to denuclearize North Korea, noting the US is still undergoing a review of its North Korea policy.

"When it comes to North Korea broadly... we will adopt a new approach -- a(n) approach that fundamentally seeks to keep the American people and our allies safe...in close coordination with our treaty allies ROK and Japan and other allies and partners on ongoing pressure options, and the future for potential diplomacy," he said.

The department official did not rule out the possibility of a summit between Biden and North Korean leader Kim Jong-un when asked, but said the new US approach toward the North will be different from that of the former Trump administration.

"Our approach will be principled. Our approach will be clear eyed. Our approach will be conducted in close coordination with our treaty allies including the Japanese and the South Koreans," said Price.

"So I'm not going to announce or, on the other hand, rule out any sort of meetings or any specific diplomatic efforts. But I think those will be the principles that guide our approach to North Korea going forward," he added.

Donald Trump held three meetings with Kim, including two bilateral summits, before he stepped down as president on Jan. 20.

North Korea has stayed away from denuclearization negotiations since the second Trump-Kim summit ended without a deal in February 2019. (Yonhap)