Robert Koepcke, deputy assistant secretary of state for Japan, Korea and Mongolia, speaks during a forum hosted by the Center for Strategic and International Studies in Washington, Feb. 12. Yonhap

A U.S. diplomat on Monday highlighted America's commitment to working in tandem with South Korea and Japan to address growing military cooperation between North Korea and Russia, which he said serves only to prolong Moscow's war in Ukraine.

Speaking at a forum, Robert Koepcke, deputy assistant secretary of state for Japan, Korea and Mongolia, also reiterated Washington's openness to dialogue with Pyongyang "without preconditions" and its willingness to discuss the reclusive regime's humanitarian issues.

"We are committed to working trilaterally as well to address DPRK-Russia military cooperation, which serves to only prolong Russia's brutal war against Ukraine, undermine the global non-proliferation regime, embolden North Korea's reckless inclinations," he told the forum hosted by the Center for Strategic and International Studies.

DPRK stands for North Korea's official name, the Democratic People's Republic of Korea.

Deepening cooperation between Pyongyang and Moscow has emerged as a major security concern as the White House has revealed the North had supplied Russia with ballistic missiles, munitions and other supplies for use in Ukraine under transactions, from which Pyongyang is thought to have also benefited militarily.

Noting the Joe Biden administration's "calibrated" approach to the North, Koepcke underscored its continued commitment to diplomacy with Pyongyang.

"We are pursuing a calibrated approach to the DPRK's escalatory actions based on the degree of the threat they pose to the United States and our allies," he said. "The United States has been clear. We seek dialogue with Pyongyang. We seek it without preconditions."

He added that the U.S. will seek to cooperate on humanitarian issues with the North regardless of its missile development program status and other concerns.

Touching on trilateral cooperation with Seoul and Tokyo, the official described it as "essential" not only for security but also for economic and other realms.

Koepcke also said that the three countries will continue to strengthen cooperation on export controls to prevent technologies from being diverted for military or "dual-use" capabilities that could potentially threaten international peace and security. (Yonhap)