A top ruling party official called Monday for South Korea to develop its own nuclear deterrent to combat the growing nuclear and missile threat from North Korea.

Support for a nuclear-armed South Korea is a minority voice in the country, but one that grows louder after every nuclear test by the North.

US tactical nuclear weapons were withdrawn from South Korea in late 1991, though the country remains under the protection of the US nuclear umbrella.

In the wake of North Korea's fourth nuclear test last month, Won Yoo-Cheol, the ruling Saenuri Party's floor leader, said it was time for the weapons to be re-deployed or for South Korea to get its own.

"We cannot borrow an umbrella from a neighbour every time it rains. We need to have a raincoat and wear it ourselves," Won was quoted as saying by the Yonhap news agency in a speech to the National Assembly.

South Korea is one of 190 signatories to the nuclear Non-Proliferation Treaty -- a pact that North Korea walked out on in 2003.

There are few takers in Washington for the idea of a nuclear-armed South Korea which would set back a longstanding, if repeatedly violated, principle of not allowing new nations into the nuclear club.

In an effort to reassure one of its key Asian allies, the US Air Force sent a nuclear-capable B-52 bomber on a sortie over South Korea shortly after the North's nuclear test on January 6.

South Korea's late military strongman Park Chung Hee -- the father of current President Park Geun Hye -- had flirted with nuclear weapons in the 1970s when then US president Jimmy Carter planned to remove American troops from the peninsula.