Theresa May is holding talks with Japanese prime minister Shinzo Abe as the crisis in North Korea comes before the UN Security Council.
Mrs May is hosting her Japanese counterpart at Chequers in what Downing Street called a "long-standing engagement" rather than a reaction to the sharp heightening of tensions on the Korean peninsula in recent weeks.
The meeting comes as Foreign Secretary Boris Johnson attends a UN Security Council session in New York to discuss the situation in North Korea.
Ahead of the gathering, Mr Johnson said Kim Jong Un was leading a "semi-deranged regime in North Korea, bent on getting nuclear weapons that could one day be used to strike this country."
The UN discussion is happening as the White House has declared that all options, including a targeted military strike, are on the table to prevent North Korea from carrying out threats against the United States and its allies in the region.
But American officials have said that a pre-emptive attack is unlikely and that US president Donald Trump's administration is pursuing a strategy of putting pressure on Pyongyang with assistance from China, North Korea's main trading partner and the country's economic lifeline.
Mrs May is expected to discuss "global issues" with Mr Abe, and Brexit is likely to feature in the talks given the level of Japanese investment in the UK.
Mr Abe is visiting Britain following talks in Russia with Vladimir Putin.