A US nuclear-powered aircraft carrier has arrived in South Korea for joint military drills between the two countries.

The USS Ronald Reagan docked in the southeastern city of Busan on Friday.

Rear Admiral Michael Donnelly, commander of the carrier strike group, said at a news conference on the vessel's deck that the group's operation in and around the Korean Peninsula illustrates the US commitment to stand together with South Korea.

He added that the operation is focused on ensuring the two countries' navies are "interoperable and integrated to face any challenge or any threat whenever required."

South Korean media reported that the two countries' navies will conduct joint exercises mainly in the Sea of Japan.

The vessel's arrival marks the first time since October 2017 that a US nuclear-powered aircraft carrier docked in South Korea for drills.

The move comes amid concerns that North Korea may conduct its seventh nuclear test. Senior foreign affairs and defense officials from the US and South Korea reaffirmed last week that a nuclear test by the North would be met with a strong and resolute response.

Observers say the show of unity between the US and South Korean militaries is apparently aimed at keeping North Korea in check, but that it could draw a sharp reaction from Pyongyang.