South Korea needs no nuclear weapons because the United States has "their back with the nuclear umbrella" and other means to defend the Asian ally from North Korea, U.S. Deputy Secretary of State Tony Blinken said Thursday.

Calls have risen in South Korea again for nuclear armament in the wake of the North's fourth nuclear test in January and a long-range rocket launch in February, with some leading members of the country's ruling party arguing that it makes no sense to rely on the U.S. "nuclear umbrella" as the North's nuclear arsenal grows.

Fueling the debate was the suggestion from U.S. Republican presidential front-runner Donald Trump that South Korea and Japan could be allowed to develop their own nuclear weapons for self-defense so as to reduce American burdens in protecting the allies.

"That debate has reemerged in South Korea as a result of North Korea's provocations. President Park (Geun-hye) was very clear in statements that she has made that that is not the path that South Korea should or will take, at least under her administration,"

Blinken said during a House Foreign Affairs Committee hearing. "And we've tried to make clear to our allies and partners that it is not necessary because to put it colloquially, we have their back with the nuclear umbrella and with every other means that we have to come to their defense."

Blinken also noted that the U.S. and the South have begun formal consultations on the potential deployment of the Terminal High Altitude Area Defense (THAAD) missile defense system to the South to better defend against threats from the North.

"We've been building up the defenses including for our partners and allies and of course, we've also been going very hard at the North Koreans on the nuclear missile program," he said. (Yonhap)