Seoul is seeking to bolster deterrence against nuclear-armed North Korea, with the South set to join a small circle of countries that operate nuclear-powered submarines after receiving US approval for the supply of restricted nuclear fuel.

"We will develop and build nuclear-powered submarines with our own technology to launch the first vessel in the mid-2030s," Defence Minister Ahn Gyu-back told a defence strategy meeting attended by President Lee Jae Myung.

Ahn said the first submarine would enter operational service "in the latter half of the 2030s".

South Korea has long sought to acquire nuclear-powered submarines to counter North Korea's growing military threats, although it had been constrained by a nuclear cooperation agreement with the United States.

Lee said in November Seoul had received Washington's approval for the construction of nuclear-powered submarines as part of a long-awaited security and trade agreement.

That included US approval for uranium enrichment and reprocessing spent fuel.

However, there had not yet been any firm indication about where the submarines would be built, with Trump saying they would be built "right here in the good ol' U.S.A.".

South Korea, which possesses nuclear reactors, said it would fulfil its nuclear non-proliferation obligations throughout the process of securing and managing low-enriched uranium for the submarines.

"The Republic of Korea maintains a firm stance that it does not possess any form of nuclear weapons and will not develop them," Ahn said.

Lee said after Ahn's briefing that nuclear-powered submarines would be "a symbol of our determination to take responsibility for peace and security on the Korean Peninsula".

US nuclear submarine technology is considered among the most sensitive and tightly guarded military secrets.