A United States nuclear-powered submarine has arrived at a port in the South Korean city of Busan amid tensions over the possible launch of an intercontinental ballistic missile (ICBM) by North Korea.

According to the South Korean Navy, the Virginia-class nuclear-powered U.S. submarine USS Missouri SSN-780 arrived at a naval base in Busan on Sunday.

The warship belongs to Submarine Squadron One of the U.S. Navy’s Pacific Fleet.

Seoul’s Navy said that it plans to promote exchanges and cooperation between the South Korean and U.S. navies and to strengthen the combined defense posture through the arrival of the submarine.

The arrival comes about three weeks after the U.S. nuclear-powered submarine USS Santa Fe arrived at a naval base on Jeju Island on November 22.

The Missouri crew plans to rest and load supplies at the Busan base.

Last Thursday, South Korea’s Principal Deputy National Security Advisor, Kim Tae-hyo, said that there is a possibility of an ICBM launch by North Korea this month.