aircraft carrier arrived in South Korea on Friday for the first time in about four years, set to join other military vessels in a show of force intended to send a message to North Korea.

USS Ronald Reagan and ships from its accompanying strike group docked at a naval base in the southern port city of Busan ahead of joint drills with South Korean forces.

"We are leaving messaging to diplomats," he said, when asked about any signal to North Korea, but added that joint drills would ensure the allies were able to respond to all threats.

South Korean President Yoon Suk-yeol has pushed for more joint exercises and other displays of military power as a warning to North Korea, which this year conducted a record number of missile tests and appears to be preparing to resume nuclear testing for the first time since 2017.

Navy aircraft carrier USS Ronald Reagan is anchored at a port in Busan, South Korea, September 23, 2022.

Officials declined to provide details of the upcoming joint drills, but said the carrier would be in port for "several days." Just hours after the ship docked, long lines of crewmembers formed as they took COVID-19 tests before being bussed into the city.

The visit is the first to South Korea by an American aircraft carrier since 2018.

The carrier visit is useful for political signalling, reassuring Seoul, and training with South Korean forces, but likely does little to further deter North Korea, said Mason Richey, a professor at Hankuk University of Foreign Studies in Seoul.