Earlier in the day, North Korea fired two short-range missiles into the sea, its first test since an impromptu meeting between US President Donald Trump and North Korean leader Kim Jong Un last month that produced an agreement to resume a working-level denuclearization dialogue.

"We want to have diplomatic engagement with North Korea, and we continue to urge the North Koreans to resolve all the things that the president and Chairman Kim have talked about through diplomacy," US State Department spokeswoman Morgan Ortagus told reporters in Washington.

But those talks have yet to begin, and North Korea warned recently they could be derailed by the United States and South Korea's refusal to scrap military exercises scheduled for next month.

"We urge no more provocations, and that all parties should abide by their obligations under (United Nations Security Council) resolutions," said Ortagus, who refused to say if she considered the missile tests "provocations."

Pyongyang carried out similar short-range launches in May, which Trump dismissed at the time as "very standard stuff" that would have no impact on his relationship with Kim.