The top U.S. commander in the Pacific warned senators Thursday that the military support that China and North Korea are giving Russia in its war on Ukraine is a security risk in his region as Moscow provides critical military assistance to both in return.

North Korea appears to have sent at least 3,000 more soldiers to Russia early this year, South Korea’s military said Thursday, demonstrating Pyongyang’s continued support for Moscow’s war on Ukraine as world leaders push for an end to the three-year conflict.