- Video report by ITV News Correspondent Angus Walker
China's president Xi Jinping has appealed for cool-headedness in a call with Donald Trump, after the US leader warned North Korea would "regret it fast" if it made any threatening move towards Guam.
State-run China Central Television quoted Xi as telling Trump the "relevant parties must maintain restraint and avoid words and deeds that would exacerbate the tension on the Korean Peninsula."
It follows days of heated rhetoric that have heightened tensions and threatened to spill over into military action
Trump has maintained military chiefs are carefully examining their options and that the US is "locked and loaded" if North Korean leader Kim Jong-un acts "unwisely".
That comes after North Korea announced it had formulated plans to fire rockets into the sea off Guam in a show of military might.
- Video report by ITV News Correspondent Juliet Bremner
The British foreign secretary Boris Johnson said the UK was working closely alongside the US to find a diplomatic solution to the crisis in a series of posts to Twitter.
He laid the blame with North Korea and said the intentional community was "shoulder to shoulder in ensuring North Korea stops its aggressive acts".
North Korea's Minju Joson newspaper, meanwhile, lashed back at the US in an editorial on Saturday.
"The powerful revolutionary Paektusan army of the DPRK, capable of fighting any war the US wants, is now on the standby to launch fire into its mainland, waiting for an order of final attack," it said.
DPRK stands for North Korea's official name, the Democratic People's Republic of Korea.
In an earlier media conference Trump told reporters: "If anything happens to Guam there is going to be big big trouble in North Korea."
Despite the heightened tensions, US defence secretary James Mattis said America was committed to a peaceful solution.
Trump also appeared to echo Mr Mattis' comments in a press conference late on Friday when he said: "Hopefully it will all work out, nobody loves a peaceful solution better than President Trump - that I can tell you."
It has also emerged that officials from both countries have been quietly holding diplomatic back-channel talks for several months.
When asked whether his bombastic comments were undermining attempts to reach a solution, Trump said: "My critics are only saying that because it's me.
"If somebody else uttered the exact same words that I uttered, they'd say, 'What a great statement, what a wonderful statement'."
The stand-off between the two countries appears to have reached its tensest point in years with a series of antagonistic comments from both sides.
It comes after rogue nuclear state North Korea appeared to have a breakthrough in weapon tests, and now reportedly has the ability to fit nuclear warheads into missiles.
Officials in Guam yesterday released official advice on how to cope with a North Korean nuclear strike, but most residents remain relatively relaxed about the threat.
ITV News Senior International Correspondent John Irvine said it would be an "an extremely provocative act" to fire missiles towards Guam, a US site which hosts a major military base.
However, if the North Koreans did shoot into the sea as outlined in their public plans, it might be hard for the Americans to calibrate a retaliation..
Guam is a sovereign US territory and hosts 3,831 military personnel.
A US Air Force spokesman from Andersen Air Force base on the island said their number one priority is to be "ready to fight tonight".
He said the Guam base deters adversaries and reassures US allies and partners in the Pacific.
"We have multiple aircraft here that are part of the continuous bomber pretense."
He added: "We feel safe here right now".
The North's threat against Guam came after Trump warned in a tweet of "fire and fury", urging North Korea to abandon its nuclear ambitions.
But the US president's rhetoric appeared to have little effect, with North Korean state media quoting Kim as calling Trump "bereft of reason" and talking a "load of nonsense".
Japan and South Korea have also vowed a strong reaction if the North were to go through with the plan to attack Guam.
Shinzo Abe, Japan's prime minister, made a public assurance on Saturday that he "will do everything, to the best of my ability, to protect the safety and property of the Japanese people" if Mr Trump tries to fire a missile over the country.
Mr Abe's statement comes in the wake of the Japanese Defence Ministry's previous announcement that it was deploying four surface-to-air Patriot interceptors in western Japan to respond to the possible risk of fragments falling from missiles.