Oct. 25 (UPI) — U.S. National Security Adviser Jake Sullivan and his counterparts from Japan and South Korea on Friday issued a joint statement voicing “grave concern” over North Korea’s move sending soldiers to Russia, possibly for use in its war against Ukraine.

Sullivan, South Korea National Security Adviser Shin Wonsik and Japanese National Security Adviser Akiba Takeo held a trilateral meeting in Washington to discuss the situation, after which the White House issued a statement focusing on North Korea.

The communist nation has sent at least 3,000 troops to eastern Russia this month, although it remains unclear what their mission is, both Washington and Seoul confirmed this week.

Sullivan, Shin, and Akiba “expressed grave concern over troop deployments by the Democratic People’s Republic of Korea to Russia, potentially for use on the battlefield against Ukraine,” the statement said.

“This deployment is the latest in a series of concerning indicators of deepening military cooperation between the DPRK and Russia, including arms and ballistic missile transfers in direct violation of United Nations Security Council resolutions.”

The trio called on Russia and North Korea “to cease these actions that only serve to expand the security implications of Russia’s brutal and illegal war beyond Europe and into the Indo-Pacific,” while also reiterating “the firm commitment of the United States, the Republic of Korea, and Japan to help Ukraine defend itself.”

The three nations also committed to coordinate support for Ukraine’s energy infrastructure, recovery and reconstruction, as well as to support “efforts to hold Russia accountable for its actions,” according to the White House.

U.S. National Security Council spokesman John Kirby said Wednesday that Pyongyang moved the troops by ship from the Wonsan area to Vladivostok, and from there they dispersed to multiple Russian sites for training.

“We do not yet know whether these soldiers will enter into combat alongside the Russian military, but this is certainly a highly concerning probability,” Kirby said at a press briefing, adding that if they are used to fight alongside regular Russian troops in Ukraine, “they’re fair game. They’re fair targets.”

Meanwhile, the three security advisers condemned North Korea’s “illicit arms transfers, malicious cyber activities, and dispatch of workers abroad to fund its unlawful weapons of mass destruction and ballistic missile programs.”

They also agreed to oppose any changes in the status quo by “force or coercion” in the waters of the Indo-Pacific, likely a reference to China’s increasingly assertive territorial claims over vast portions of the South China Sea.