U.S. President Donald Trump will hold telephone conversations with Prime Minister Shinzo Abe and Chinese President Xi Jinping on Sunday (Monday morning Japan time), a White House official said, amid heightened tensions surrounding North Korea.

Pyongyang is thought to be preparing to conduct further test-firings of missiles or a sixth nuclear test, possibly on the 85th anniversary of the founding of the Korean People's Army on Tuesday.

Trump and his senior officials have said that all options, including military action, are "on the table" in dealing with North Korea's pursuit of ballistic missiles and nuclear weapons, which violate U.N. Security Council resolutions.