Another nuclear-powered U.S. submarine, the second in a week, docked in South Korea on Monday.
According to the South Korean Navy, USS Annapolis, a Los Angeles-class submarine, docked at a naval base in the country's southern island of Jeju on Monday, Seoul-based Yonhap News reported.
It comes amid rising tensions on the Korean Peninsula as Seoul boosted its relations with the U.S. and Japan and held regular off and on-shore drills in the region.
North Korea has itself ramped up missile launches, threatening a pre-emptive strike.
It fired multiple cruise missiles on Saturday into the Yellow Sea between China and the Korean Peninsula, according to Seoul.
The South Korean Navy said the USS Annapolis has arrived "for replenishment purposes."
"Its entry into the port is to replenish military supplies while on an operations mission," the navy said in a text message sent to journalists.
The key mission of the USS Annapolis "is to conduct operations for anti-ship and anti-submarine warfare."
Last week on Tuesday, the USS Kentucky docked in Busan port, 320 kilometers (198 miles) southeast of Seoul. It left South Korea on Friday.
It was the first time since 1981 that any U.S. nuclear-powered submarine had visited the region.
