U.S., Japanese and South Korean naval forces exercised together in East Asian waters on Thursday in their most complex and final joint drills before President Joe Biden hands over one of his signature national security initiatives to Donald Trump.

North Korea’s deployment of troops to Russia to support Russia’s war in Ukraine, as well as North Korea’s nuclear weapons program and dimming prospects for a peaceful resolution to a decades-long conflict with South Korea are also raising tensions in Asia.

U.S. President Joe Biden met with Japanese and South Korean leaders on Friday as they sought to cement their diplomatic progress ahead of a new Trump administration that many fear could upend alliances worldwide.