Chinese leader Xi Jinping urged United States President Donald Trump on Saturday to avoid rhetoric that could inflame tensions with North Korea as an escalating war of words raised global alarm.

Xi made the plea in a phone call hours after Trump ramped up his warnings to Pyongyang, saying the Stalinist regime would “truly regret” taking hostile action against the United States.

The White House said in a statement that the two leaders “agreed North Korea must stop provocative and escalatory behaviour” and that they are both committed to the denuclearisation of the peninsula.

But the Chinese foreign ministry said Xi urged Trump to avoid “words and deeds” that would “exacerbate” the already-tense situation, exercise restraint and seek a political settlement.

Trump has been engaged all week in verbal sparring with the North over its weapons and missile programmes, as US media reported Pyongyang has successfully miniaturised a nuclear warhead.

The Republican party billionaire has progressively ramped up the tone throughout the week and on Friday declared that the US military is “locked and loaded.”

In a call with Guam Governor Eddie Calvo on Friday, Trump said the US military is prepared to “ensure the safety and security of the people of Guam” in response to Pyongyang's plans to launch missiles towards the Pacific territory.

Japanese media said Tokyo was deploying its Patriot missile defence system following Pyongyang's threat to fire ballistic missiles over the country towards Guam.

'Fire and fury'

In another move that could further fan the flames, satellite photos posted by defence expert Joseph Bermudez suggested that North Korea could be preparing for fresh submarine-based ballistic missile tests.

Trump had earlier brandished a threat of unleashing “fire and fury” on Pyongyang, then noted on Thursday maybe that statement “wasn't tough enough.”

China, North Korea's biggest ally and trade partner, has been voicing concern at the mounting exchanges and a state-run newspaper suggested that Beijing should stay neutral if Pyongyang struck the US first.

Previously accused by Trump of not doing enough to rein in the authoritarian regime, China voted in favour of a series of wide-sweeping UN Security Council sanctions against North Korea last weekend.

According to the Chinese foreign ministry, Trump told Xi over the phone that he “fully understands China's role in the nuclear issue in the Korean Peninsula.” Trump is expected to visit China later this year.

The North's official KCNA news service in an editorial blamed Trump for “driving the situation on the Korean peninsula to the brink of a nuclear war,” calling the US “the heinous nuclear war fanatic.” The sabre-rattling has sparked worldwide concerns that a miscalculation by either side could trigger a catastrophic conflict on the Korean Peninsula.

Russia and Germany have also urged both sides to tone down the rhetoric.

“Military solutions are now fully in place, locked and loaded, should North Korea act unwisely. Hopefully Kim Jong Un will find another path!” Trump wrote Friday from his golf club retreat in New Jersey, where he is on a working vacation.

Moscow 'alarmed'

Russia's Foreign Minister Sergei Lavrov said Moscow was “very alarmed” at Trump's tough talk, and said Washington should take the first step toward cooling tensions.

“When a fight has nearly broken out, the first step away from the dangerous threshold should be taken by the side that is stronger and smarter,” Lavrov said.

German Chancellor Angela Merkel said diplomacy was the answer. “Germany will very intensively take part in the options for resolution that are not military but I consider a verbal escalation to be the wrong response,” she said.

Nearly a week ago, the UN Security Council unanimously passed fresh sanctions against Pyongyang over its weapons programme, including export bans, a new punishment that could cost North Korea $1 billion a year.

“This is clearly a time for all the parties to focus on how to de-escalate and lower the tensions,” said the spokesman for UN Secretary General Antonio Guterres.

Tensions on the peninsula tend to increase when Seoul and Washington launch major military joint exercises, and the next, Ulchi Freedom Guardian, is set to kick off around August 21.

'Tragedy of war'

US Defense Secretary Jim Mattis appeared intent Thursday on easing the tension, describing the prospect of war as “catastrophic” and saying diplomacy remained the priority.

Asked if Mattis was aware of Trump's latest tweet, spokesman Colonel Rob Manning simply said the Pentagon chief was “in close and constant contact with the president.”

A White House official noted: “There are military plans for just about any crisis we may face in the world. (...) This isn't anything new.”

Relations between Washington and Pyongyang have been tense for months, in the wake of the North's repeated missile tests, including two successful intercontinental ballistic missile (ICBM) test launches in July that are believed to have brought much of the US mainland within range.

North Korea raised hackles in the United States when it announced a detailed plan to send four missiles over Japan and towards Guam, an island territory of some 165,000 people, where some 6,000 US soldiers are based.