U.S. President Joe Biden plans to urge Chinese President Xi Jinping to work to restrain North Korea's nuclear and missile provocations when they meet in Indonesia next week, a senior U.S. official said Saturday.

North Korea will also be a key topic when Biden meets with his Japanese and South Korean counterparts as part of a flurry of diplomacy taking place on the fringes of international meetings in Southeast Asia, according to National Security Adviser Jake Sullivan.

Sullivan said he expects "enhanced" security cooperation to be agreed on during the trilateral talks.

Biden will meet with Xi on the sidelines of a summit of the Group of 20 major economies on the resort island of Bali. His trilateral meeting with Japanese Prime Minister Fumio Kishida and South Korean President Yoon Suk Yeol will be held in Cambodia on Sunday.

While the Biden-Xi meeting is expected to touch on a range of regional and global issues, including Taiwan, the U.S. president will "certainly raise the issue of North Korea" as Pyongyang carries out ballistic missile tests at an unprecedented pace this year, Sullivan told reporters.

Pyongyang is also believed to have made preparations for what would be first its nuclear test since September 2017 and seventh overall.

Biden plans to tell Xi that North Korea represents "a threat" not just to the United States and its closest allies in Asia, but to "peace and stability across the entire region," Sullivan said.

"If North Korea keeps going down this road, it will simply mean further enhanced American military and security presence in the region," he added, saying China therefore "has an interest in playing a constructive role in restraining North Korea's worst tendencies."

Following the three-way meeting between Biden, Kishida and Yoon, a statement is likely to be issued, which Sullivan said he hopes will set out "an elevated level" of trilateral engagement.

While noting that Japan and South Korea have a number of issues they "constantly grapple with bilaterally," the goal from the U.S. perspective is to ensure that "at a trilateral level, we are maximizing our capacity to work together" on critical security issues, Sullivan said.

Relations between Japan and South Korea sank to their lowest level in decades under Yoon's progressive predecessor Moon Jae In over disputes stemming from Japan's 1910-1945 colonial rule of the Korean Peninsula, including compensation demands from South Koreans over wartime labor.

But the two East Asian neighbors appear to be in the process of improving their bilateral ties, after Yoon, a conservative, took office in May with a pledge to take a future-oriented approach toward relations with Japan.

Biden, Kishida and Yoon also met in Spain in June, making it the first such gathering among the leaders of the three countries since 2017.

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