U.S., South Korean, and Japanese officials issued a joint statement on Monday strongly condemning deepening military cooperation between North Korea and Russia. The officials criticized North Korea’s arms transfers to Russia and expressed concern over a strategic partnership treaty signed during Russian leader Vladimir Putin’s visit to Pyongyang last week.

The statement warned that the North Korea-Russia partnership threatens stability in Northeast Asia and Europe and violates U.N. Security Council resolutions. The U.S., South Korea and Japan pledged to strengthen diplomatic and security cooperation to counter North Korean threats. They reaffirmed the U.S. defense commitment to South Korea and Japan as “ironclad” while urging North Korea to cease provocations and return to negotiations.