U.S. Vice President Joe Biden has told Chinese President Xi Jinping that Japan has the capacity to acquire nuclear weapons “virtually overnight.”

Speaking at a Public Broadcasting Service program aired Monday, Biden said he had urged Xi to exert influence on North Korea so it will abandon its missile and nuclear weapons developments.

Referring to Pyongyang’s recent nuclear test and missile launches in violation of U.N. Security Council resolutions, Biden said that if China and the United States fail to take effective action against North Korea, “What happens if Japan, who could go nuclear tomorrow? They have the capacity to do it virtually overnight.”

Biden did not say when his conversation with Xi took place.

The vice president said China “has the single greatest ability to influence North Korea by cutting off A, B, C, D, a whole range of things, but it also could cause the implosion of North Korea.”

Biden said North Korea is building nuclear weapons that can strike as far as away the U.S. mainland. “And I say, so we’re going to move up our defense system,” he said, suggesting Washington intends to deploy an advanced U.S. missile interception system called Terminal High Altitude Area Defense, or THAAD, in South Korea.

The vice president quoted Xi as saying, “Wait a minute, my military thinks you’re going to try to circle us,” underscoring China’s opposition to the deployment of THAAD in South Korea.

Biden dismissed Republican presidential candidate Donald Trump’s view that he is open to the idea of both Japan and South Korea developing their own nuclear weapons and would be willing to withdraw U.S. troops from their soil.

“It’s okay with Donald Trump. But it’s not okay for us to continue to see the proliferation of nuclear weapons around the world,” he said.

Asked about Biden’s remarks, Japanese Deputy Chief Cabinet Secretary Hiroshige Seko said at a news conference Friday in Tokyo that Japan “can never possess nuclear weapons.”

Seko said the three non-nuclear principles of not producing, possessing or allowing nuclear weapons on Japanese territory are an important basic policy of the Japanese government.