The White House on Wednesday rejected Republican presidential front-runner Donald Trump's idea of allowing South Korea to go nuclear in response to North Korean threats, saying it could give Pyongyang justification for its nuclear development.

"That prospect would be incredibly destabilizing," White House press secretary Josh Earnest said. "Right now, the policy of the United States, a policy that is strongly supported by the broad international community, is that we should denuclearize the Korean Peninsula."

Trump first broached the idea in an interview published Friday, arguing that the U.S. is no longer rich enough to defend other countries and the possibility of allowing the allies to go nuclear is something that "we have to talk about."

He repeated the point again during a town hall meeting televised on CNN Tuesday night.

"Mr. Trump's suggestion that somehow we should encourage our allies in South Korea to develop nuclear weapons is directly contrary to a policy that the United States has long pursued and is directly contrary to a policy that the international community has long supported," Earnest said.

"And it's hard for me to imagine why it would be a good idea to give the North Koreans any justification or any incentive to further accelerate their nuclear weapons program. It doesn't make any sense," he said. "What protects South Korea and Japan is knowing that they have the steadfast support of the most powerful country in the world."

The U.S. will stand shoulder-to-shoulder with the allies as they confront nuclear menacing from the North, he said. 

Earnest also took a swipe at Trump.

"It is why it's particularly important that our country is led by a commander in chief who understands the consequences of his words and his policy decisions," he said. (Yonhap)