But he later insisted that "nobody loves a peaceful solution better than President Trump".
According to Chinese state media, Mr Xi told Mr Trump in a phone call that "all relevant parties" should stop "words and deeds" that would exacerbate the situation.
Meanwhile, China has reiterated calls for all sides to maintain calm and reduce tensions over the Korean Peninsula. The possibility of escalation is made even more acute by the lack of any means of official communication across the Demilitarized Zone, though there has been no easing of the barrage of inflammatory comments in the US and the North since new sanctions against North Korea were announced last week. She says she'd like see the president's tough talk dial down.
German Chancellor Angela Merkel said there was no military solution, and "an escalation of the rhetoric is the wrong answer".
When asked if it was a good idea for the president to threaten "fire and fury" on North Korea, Mr Green said: 'I think the sensible way for people to proceed is to work through the United Nations process, that's what the British Government has been supporting and will continue to support'.
In a call with Guam Governor Eddie Calvo yesterday, Mr Trump said the USA 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. "They will be met with fire and fury like the world has never seen".
Nor is it clear that the North Koreans would actually want to wipe Guam off the map, even if they could. However, "the bigger threat", he said, "is accidentally stumbling into war", which is possible, given "the incoherent signally from the [Trump] administration".
Tensions escalated on the peninsula after the DPRK test-fired what it called intercontinental ballistic missiles, known as Hwasong-14, twice last month. It just engineered a UN Security Council resolution that by sanctioning the export of North Korean coal, iron ore, and foreign workers could cost the regime one-third of its export earnings.
The defense ministry deployed the Patriot Advanced Capability-3 (PAC-3) system in Shimane, Hiroshima and Kochi in western Japan, which North Korea had warned could be along its missiles' flight path, public broadcaster NHK and Kyodo News said.
There has been no indication that any actual attack on the Pacific island is imminent.
The comments from the influential Global Times came after Trump stepped up his rhetoric on Thursday against North Korea, saying his earlier threat to unleash "fire and fury" on Pyongyang if it launched an attack may not have been tough enough.
At least 1,000 of those weapons are capable of reaching the densely populated South Korean capital Seoul and its metropolitan area, home to some 25 million people.
He added, "We have an Anzus agreement", referring to the security treaty between Australia, the United States and New Zealand.
He also chided the North's closest ally, China, saying it could do "a lot more".
Soon after the United Nations resolution, North Korea accused the USA of "trying to drive the situation of the Korean peninsula to the brink of nuclear war", according to reports.