The upcoming trilateral summit between South Korea, the United States and Japan in Peru will be a chance for the three countries to discuss a "coordinated" response to North Korea's troop dispatch to support Russia's war in Ukraine, a senior US security official said Thursday.

National Security Advisor Jake Sullivan made the remarks as South Korean President Yoon Suk Yeol, US President Joe Biden and Japanese Prime Minister Shigeru Ishiba are set to hold a trilateral summit on the margins of the Asia Pacific Economic Cooperation summit in Lima on Friday.

"It will also be an opportunity to get a coordinated response to the introduction of DPRK soldiers onto or into western Russia," Sullivan said in a press briefing, referring to the official name of North Korea.

He added that the summit will be a chance for the three leaders to make sure that their countries are "on the same page" and moving out "in a coordinated way."

"This is a significant development, and we are going to treat it with the seriousness, with which it deserves to be treated," he said.

Seoul and Washington have confirmed that North Korean troops have begun engaging in combat operations alongside Russian forces in the fighting against Ukraine -- a development that observers say could expand the war in Ukraine, and will have security implications for Europe and the Indo-Pacific.

US officials have said more than 10,000 North Korean troops have been deployed to Russia with Russians having trained them in artillery, unmanned aerial vehicle and basic infantry operations, including trench clearing operations.

Further commenting on North Korea, Sullivan said the upcoming three-way summit will be a "real" opportunity to discuss activities by the recalcitrant regime, stressing Washington remains vigilant for the "ever-present" possibility of a seventh North Korean nuclear test and other provocative acts.

"Obviously, it's a real opportunity for us to consult at the leaders' level both to be prepared for any provocation that may come, whether it be with respect to missile testing or a nuclear test or other provocations," he said.

Responding to a question about Pyongyang being relatively quiet after the election period, Sullivan said, "I do not think we can count on a period of quiet with the DPRK." He also underscored the US' vigilance against potential North Korean provocations.

"The possibility of a seventh nuclear test remains ever present. It's something we are vigilant for," he said.

"Transitions have historically end time periods when the DPRK has taken provocative actions both before and after the transition from one president to a new president. So that's something we are watching very carefully." (Yonhap)