The president said stronger ties with South Korea and Japan are working, but did not address whether President-elect Donald J. Trump would continue his approach when he takes office in January.

The recently signed mutual defense treaty could be used to justify thewidening of the war in Ukraine, as the U.S. says North Korean and Russian troops are already battling Ukrainian forces.

Observers believe both countries aim to take advantage of a perceived leadership void during the U.S. presidential transition to push their immediate objectives on the battlefield.