The White House on Monday poured more cold water on potential talks with North Korea over its nuclear weapons program just days after U.S. Secretary of State Rex Tillerson said Washington was in direct contact with leader Kim Jong Un's regime.

The move came as North Korean state media threatened Japan with "nuclear clouds" and lambasted Prime Minister Shinzo Abe's push for maximum pressure on the isolated nation.

"Now is not the time to talk," White House spokeswoman Sarah Sanders said Monday, further reinforcing President Donald Trump's view that Tillerson was "wasting his time trying to negotiate with Little Rocket Man," a mocking reference to Kim.