China warned against "troublemaking" on its doorstep, in an apparent rebuke to North Korea, and the United States said it was postponing a missile test to help calm high tension on the divided Korean peninsula.
But in the midst of what some described as an unprecedented ratcheting up of rhetoric from Beijing, China began running into criticism from influential political voices in Washington who blamed North Korea's closest ally for not doing enough to avert the danger of conflagration.
The North, led by 30-year-old Kim Jong-un, has been issuing vitriolic threats of war against the United States and U.S.-backed South Korea since the United Nations imposed sanctions in response to its third nuclear weapon test in February.
Pyongyang's anger appears heightened by U.S.-South Korean joint military exercises. But most analysts say it has no intention of starting a conflict that would bring its own destruction and instead is out to wring concessions from a nervous international community.
The North told diplomats late last week to consider leaving Pyongyang because of the tension, but embassies appeared to view the appeal as more rhetoric and staff have stayed put.
South Korea said it was ready for any kind of action that the North's unpredictable leaders might make - including a possible missile launch - by Wednesday, after which the North said it could not guarantee diplomats' safety.
China, North Korea's sole financial and diplomatic backer, has shown growing irritation with Pyongyang's warnings of nuclear war.
Chinese President Xi Jinping, addressing a forum on the southern island of Hainan, did not name North Korea but said no country "should be allowed to throw a region and even the whole world into chaos for selfish gain".
Stability in Asia, he said, "faces new challenges, as hot spot issues keep emerging and both traditional and non-traditional security threats exist".
Chinese Foreign Minister Wang Yi expressed similar frustration in a statement late on Saturday, relating a telephone conversation with U.N. Secretary-General Ban Ki-moon.
"We oppose provocative words and actions from any party in the region and do not allow trouble making on China's doorstep," Wang said, according to a ministry statement on its website.
On Sunday, the ministry expressed "grave concern" at rising tension and said China had asked North Korea to "ensure the safety of Chinese diplomats in North Korea, in accordance with the Vienna Convention and international laws and norms".
China's embassy, it said, was "understood" to be operating normally in Pyongyang.
The White House had no immediate comment on China's statements.
Former U.S. Ambassador to China Jon Huntsman said Xi's comments were unprecedented for the North Korea crises that have flared periodically in recent history.
"It suggests to me, as I've watched the ratcheting up of frustration among Chinese leaders over the last many years, that they've probably hit the 212-degree boiling point as it relates to North Korea," he told CNN on Sunday.
U.S. senators expressed disappointment in China's response.
Republican Senator John McCain, a member of the Senate Armed Services Committee, criticized China's "failure to rein in what could be a catastrophic situation" and said Beijing could step up pressure by using its influence over North Korea's economy.
"Chinese behavior has been very disappointing," McCain said on CBS's "Face the Nation" program.
"More than once, wars have started by accident and this is a very serious situation," he added. "South Korea would win. We would win if there was an all-out conflict. But the fact is that North Korea could set Seoul on fire. And that obviously would be a catastrophe of enormous proportions."
Senator Chuck Schumer, an influential Democrat, agreed with McCain on the same program. Republican Senator Lindsey Graham blamed China for the current crisis, telling NBC's "Meet the Press" that Beijing is propping up a "crazy regime" for fear that reunification would leave a "democratic Korea" next door.
Leaders from Australia and Britain stressed the need for a clear international response that would avoid an armed conflict. Switzerland's Foreign Ministry offered to mediate.
Kim, the third member of his dynasty to rule North Korea, is thought to have spent several years in Switzerland being educated under a pseudonym. He took over in December 2011 after the death of his father, Kim Jong-il, who confronted South Korea and the United States throughout his 17-year rule.
In Washington, a defense official said a long-scheduled test of the Minuteman III intercontinental missile, due to take place at the Vandenberg Air Force Base in California, would be postponed.
"This test ... has been delayed to avoid any misperception or miscalculation in light of recent tensions on the Korean peninsula," the official said on Saturday. "This is the logical, prudent and responsible course of action to take."
The South Korean president's office said the country had a "firm military readiness" for any eventuality. It described as "planned behavior" the North's call for South Korean workers to leave the Kaesong joint industrial park, just inside North Korea, and for diplomats to evacuate Pyongyang by Wednesday.
South Korean media said on Friday the North had moved two medium-range missiles to the country's east coast, but there has been no confirmation of such a move.
The North has always condemned joint exercises off the South Korean coast, but its rhetoric has been especially furious this year as the United States sent nuclear-capable stealth bombers from their home bases.
North Korean state television showed a military training session, with soldiers putting dogs through their paces, including one seen tearing to pieces an effigy of South Korean Defense Minister Kim Kwan-jin. Soldiers were shown firing at pictures of the minister and a depiction of a U.S. serviceman.
"As you all know, on the Korean peninsula, it is not a matter of whether we will have a war or not, but whether it will take place today or tomorrow," an unidentified soldier said.
There was no evidence of any tension in the South Korean capital, Seoul, with residents strolling in the city centre on a chilly spring day.
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