A U.S. nuclear-powered submarine has arrived at a naval base in the southern port city of Busan.

According to South Korea’s Naval Operations Command on Monday, the USS Alexandria, a Los Angeles-class attack submarine, entered the naval base in Busan in the morning to replenish supplies and allow its crew to rest.

The Navy said it plans to promote exchanges and cooperation with the U.S. navy and to enhance their joint defense posture. 

It marks the first time the six-thousand-ton USS Alexandria has entered South Korea.