President Donald Trump is escalating his rhetoric on North Korea, saying his "fire and fury" comment might not be "tough enough".
"Maybe that statement wasn't tough enough," Trump told reporters on Thursday as he prepared to meet with top national security advisers. "If anything, that statement may not be tough enough."
His comments are the latest in a series of trades between the president and the rogue state, which earlier said on Thursday it plans to fire four intermediate-range missiles over Japan to land near the US Pacific island territory of Guam.
North Korea's army will complete the plans in mid-August, when they will be ready for leader Kim Jong Un's order, state-run KCNA news agency reported on Thursday.
The plans call for the missiles to land in the sea just 30-40km from Guam.
North Korea announced the plans in reaction to Trump's comments on Tuesday that any threats by Pyongyang would be "met with fire and fury like the world has never seen", remarks that KCNA called "a load of nonsense".
As announced by North Korea, which added detail to a plan first unveiled on Wednesday, the planned path of the missiles would cross some of the world's busiest sea and air traffic routes.
- Cops filmed dancing with swingers before Melbourne nightclub shooting
- Passengers trapped after London double-decker bus ploughs into building
North Korea's apparently rapid progress in developing nuclear weapons and missiles capable of reaching the US mainland has fuelled tensions that erupted into a war of words between Washington and Pyongyang this week, unnerving regional powers and global investors.
World stocks fell for a third day, with shares in Seoul slumping to a seven-week low.
Experts in South Korea say North Korea's plans ratchet up risks significantly, since Washington is likely to view any missile aimed at its territory as a provocation, even if launched as a test.
North Korea has carried out a series of missile and nuclear bomb tests in defiance of the international community.
While North Korea regularly threatens to destroy the United States and its allies, the report was unusual in its detail. It follows two successful tests of an intercontinental missile by the isolated state in July and a series of other missile tests.
Angered as the US and its allies ignore Chinese calls to calm tensions over North Korea, and distracted by domestic concerns, China is largely sitting out the crisis.