U krainian President Volodymyr Zelensky said North Korea is preparing to send 10,000 troops to help Russia’s war on Ukraine, in a sign of deepening military cooperation between Moscow and Pyongyang.

Russia’s army is forming a unit of some 3,000 North Koreans, a Ukrainian military intelligence source has told the BBC, in the latest report suggesting that Pyongyang is forming a close military alliance with the Kremlin.

The U.S. and its allies are “alarmed” by North Korea’s nuclear and missile threats as well as its increasing military support for Russia’s war in Ukraine, a senior U.S. official said Wednesday, but couldn’t confirm Ukrainian claims that North Korean soldiers were sent to fight for Moscow.