A US nuclear-powered submarine on Friday made a port call at a city in southeast South Korea, Yonhap news agency reported Friday.
The deployment of US strategic military assets to South Korea came amid the heightened tensions on the Korean Peninsula following the Democratic People's Republic of Korea's (DPRK) sixth nuclear test in September.
During the visit sailors will experience the culture and history of South Korea as well as foster outstanding relations between the US Navy, Korean military and the local Busan community.
President Donald Trump has threatened to "totally destroy" the North if forced to defend the US or its allies.
The U.S. Navy said the submarine is capable of "supporting Special Operation Forces (SOF) missions" and providing "unprecedented strike and special operation mission capabilities from a stealthy, clandestine platform".
Its homeport is Bremerton, Washington, but the submarine is based in the US Pacific island territory of Guam - which has repeatedly been threatened by despot Kim Jong Un.
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The Los Angeles-class attack submarine the USS Tucson (SSN 770) pulled into the U.S. Fleet Activities Chinhae base on October 7 "as part of its deployment to the Indo-Asia-Pacific region", the U.S. Navy said on Tuesday.
It also has conducted six underground nuclear tests since 2006, including its most recent and powerful on September 3.
A U.S. nuclear-powered fast-attack submarine arrived in South Korea last weekend as part of its regional deployment, the USA military announced Wednesday.
"The training is a regular combined one to prepare for the threat of various maritime provocations by North Korea and to strengthen interoperability between the South and the U.S.", Vice Admiral Jung Jin-sup, South Korean chief of naval operations, said in a written statement.
"Today, our relationship is stronger than it has ever been and our ironclad partnership is further reinforced by this visit from MI".
About 28,500 USA servicemembers are based in South Korea, which remains technically at war with the North after the three-year war ended in an armistice instead of a peace treaty.