WASHINGTON, Oct 23 - The U.S. said Wednesday that 3,000 North Korean troops have been deployed to Russia and are training at several locations, calling the move very serious and warning that those forces will be “fair game” if they go into combat in Ukraine.

The deployment raises the potential for the North Koreans to join Russian forces in Ukraine and suggests expanded military ties between the two nations as Moscow seeks weapons and troops to gain ground in a grinding war that has stalemated after more than two years, The Associated Press reported.