Theresa May has spoken with Donald Trump to agree the need for "swift" measures to tackle the nuclear threat of North Korea.
The Prime Minister spoke with Mr Trump in a phone call after which they urged China to do all in its power to deter the rogue state from further provocation.
It comes after ministers were warned during their regular Cabinet meeting that Kim Jong-un's nuclear weapons are stationed closer to London than they are to Los Angeles.
Following the trans-Atlantic call, a Downing Street spokesman said: "Ms 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 spokesman also said: "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."
Kim Jong-un inspects weapon North Korea says is powerful hydrogen bomb
Show all 6Foreign Secretary Boris Johnson also told MPs China needed to try and end the stand off on the Korean peninsula.
He said: "China, which accounts for 90 per cent 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."
Earlier in the day Ms May, Mr Johnson and other cabinet ministers met to discuss the on-gong situation, during which time they were warned in a briefing that Pyong Yang is closer to London than Los Angeles.
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