A U.S. nuclear-powered aircraft carrier docked in the South Korean port city of Busan over the weekend, a visit that Seoul described as a demonstration of Washington’s commitment to providing extended deterrence against North Korean threats.

The arrival of the USS Theodore Roosevelt and assets of the U.S. Carrier Strike Group Nine, including Aegis destroyers USS Halsey and USS Daniel Inouye, at Busan Operational Base on Saturday came days after Vladimir Putin and Kim Jong Un signed a mutual defense treaty in Pyongyang.