...The USS Ronald Reagan carrier strike group is set to arrive at a naval base in Busan, 390 kilometers south of Seoul, on Friday, as the allies are sharpening security coordination amid concerns about the possibility of the North conducting a nuclear test or other provocations.

"By conducting combined drills, the Navies of the two countries plan to strengthen their military readiness and demonstrate the firm resolve of the South Korea-U.S. alliance for peace and stability on the Korean Peninsula," the Navy said in a press release.

The strike group consists of three vessels -- the Nimitz-class carrier, the USS Chancellorsville guided-missile cruiser and the USS Barry Aegis-equipped destroyer.

The USS Annapolis, a nuclear-powered submarine, will also take part in the allies' drills, according to a South Korean government source.