Donald Trump and Theresa May have agreed North Korea is “a threat to global peace” in a phone call on the ongoing nuclear crisis.
Downing Street said the pair agreed on the need for more sanctions and more pressure from China.
A Number 10 spokesman said: “Theresa May today spoke with President Trump to discuss North Korea’s most recent missile tests, which have been conducted against all standards of international behaviour.
“The Prime Minister stressed that the regime poses a threat not simply to its region but to global peace and security, and it was important for the international community to send out a clear message that such irresponsible and provocative actions must end.
“Mrs May said Britain would work with the US and international partners to continue to exert economic pressure on North Korea through further measures including sanctions.
“The Prime Minister noted the importance of the UN Security Council continuing to present a strong and unified international voice by reaching swift agreement on new measures.
“The Prime Minister said she would also work with EU leaders on further measures the EU could take to pressure the North Korean regime.
“The Prime Minister and the President agreed on the key role which China has to play, and that it was important they used all the leverage they had to ensure North Korea stopped conducting these illegal acts so that we could ensure the security and safety of nations in the region.
“During the call, the Prime Minister also extended her condolences to the President and the US public for the loss of life and damage caused by Hurricane Harvey and expressed the UK’s solidarity with the US people at this time.”
It comes as Foreign Secretary Boris Johnson said China must use all its influence to end “nuclear blackmail” from North Korea.
Johnson told MPs Britain was at the heart of international efforts to bring about a diplomatic solution after Pyongyang said it had detonated a hydrogen bomb at the weekend.
The Foreign Secretary told the House of Commons: “China, which accounts for 90% of North Korea’s overseas trade, has a unique ability to influence the regime - and the House can take heart from the fact that Beijing voted in favour of the latest sanctions resolution and condemned Pyongyang’s actions in the most unsparing terms.
“I call on China to use all of its leverage to ensure a peaceful settlement of this grave crisis.”
Johnson said the rogue state’s latest nuclear test was a matter of global concern.
“At noon on Sunday, local time, North Korea tested the most powerful nuclear device ever detonated in the history of the regime’s quest for an illegal arsenal.
“The regime claimed to have exploded a hydrogen bomb capable of being delivered on an intercontinental ballistic missile.
“We should treat that claim with scepticism, but the House must be under no illusion that this latest test marks another perilous advance in North Korea’s nuclear ambitions.”
Commending the “dignity and restraint” shown by South Korea and Japan despite both countries being “in the firing line of Pyongyang’s reckless ambitions”, the Foreign Secretary said there had been a “steady drumbeat of provocative and dangerous actions by Kim Jong-un’s regime”.
Criticising North Korea’s “brazen defiance” of the rest of the world, Johnson said: “Just as North Korea has pursued nuclear weapons with single-minded determination, so the international community must show the same resolve in our pursuit of a diplomatic solution.”
Johnson’s comments came after North Korea’s ambassador in London, Choe Il, was summoned to the Foreign Office for a dressing down from Asia minister Mark Field.
Following the meeting, Field said: “North Korea’s reckless actions have created a deeply dangerous and unstable situation.
“I urge the regime to end its illegal pursuit of nuclear and ballistic missiles and return to dialogue with the international community.”
Prime Minister Theresa May told a meeting of the Cabinet on Tuesday that North Korea’s nuclear and ballistic missile programmes represent a “threat to the whole of the international community”.
Speaking to senior Government ministers at their first meeting after Parliament’s summer break, Mrs May vowed that Britain would continue to work with international partners to put pressure on Pyongyang to turn away from its current course.
Downing Street has stressed Britain’s “overwhelming” preference for a peaceful diplomatic resolution to the crisis.
Meanwhile, Former Foreign Secretary Lord Hague has cautioned that Mr Trump’s threats of “fire and fury” will not deter Kim from continuing with his nuclear programme.
Writing in the Daily Telegraph, Lord Hague said: “There are no sanctions that will deter him... necessary as they are to demonstrate international disapproval.
“Nor will threatening ‘fire and fury’ or saying ‘talking is not the answer’ as President Trump did, because Kim will calculate that the US will not start a war that could be so catastrophic all round, and the stronger he gets the less likely they will be to do so.”
In a tweet, Trump said: “I am allowing Japan and South Korea to buy a substantially increased amount of highly sophisticated military equipment from the United States.”
The PM also intends to telephone French president Emmanuel Macron for talks on the crisis.