A North Korean missile 'blew up almost immediately' on its test launch on Sunday, the U.S. Pacific Command said.
The test took place just hours before U.S. Vice President Mike Pence landed in South Korea for talks on the North's increasingly defiant arms program.
The failed launch from North Korea's east coast, ignoring admonitions from major ally China, came a day after North Korea held a grand military parade in its capital, marking the birth anniversary of the state founder, displaying what appeared to be new long-range ballistic missiles.
South Korea said the combined show of force 'threatened the whole world' but a U.S. foreign policy adviser traveling with Pence on Air Force Two appeared to defuse some of the tension, saying the test of what was believed to be a medium-range missile had come as no surprise.
'We had good intelligence before the launch and good intelligence after the launch,' the adviser told reporters on condition of anonymity.
'It's a failed test. It follows another failed test. So really no need to reinforce their failure. We don't need to expend any resources against that.'
The adviser said the missile's flight lasted four or five seconds.
'It wasn't a matter of if, it was a matter of when. The good news is that after five seconds it fizzled out.'
Pence is in Seoul at the beginning of a 10-day trip to Asia in what his aides said was a sign of U.S. commitment to its ally in the face of rising tension.
The U.S. nuclear-powered USS Carl Vinson aircraft carrier strike group is also heading to the region.
A U.S. Navy attack on a Syrian airfield this month raised questions about U.S. President Donald Trump's plans for reclusive North Korea, which has conducted several missile and nuclear tests in defiance of U.N. sanctions, regularly threatening to destroy the South and the United States.
South Korea, which hosts 28,500 U.S. troops, warned of punitive action if the Sunday launch led to further provocation.
'North Korea showing a variety of offensive missiles at yesterday's military parade and daring to fire a ballistic missile today is a show of force that threatens the whole world,' South Korea's Foreign Ministry said in a statement.
The North has warned of a nuclear strike against the United States if provoked. It has said it has developed and would launch a missile that can strike the mainland United States but officials and experts believe it is some time away from mastering the necessary technology, including miniaturizing a nuclear warhead.
The timing of the test, coinciding with Pence's trip and a day after the military parade, would suggest deliberate defiance.
The North launched a ballistic missile from the same region this month, ahead of a summit between the United States and China in Florida to discuss the North's arms program.
But that missile, which U.S. officials said appeared to be a liquid-fuelled, extended-range Scud, only flew about 60 km (40 miles), a fraction of its range before spinning out of control.
Tension had escalated sharply amid concern the North may conduct a sixth nuclear test or a ballistic missile test launch around Saturday's 105th birth anniversary of founding father Kim Il Sung that it calls the 'Day of the Sun'.
The White House has said Trump has put the North 'on notice'.
China, which Trump has urged to do more to rein in North Korea, has spoken out against its missile and nuclear tests and has supported U.N. sanctions. It has repeatedly called for talks to defuse the crisis.
China's top diplomat, Yang Jiechi, and U.S. Secretary of State Rex Tillerson exchanged views on the "situation on the Korean peninsula" by phone on Sunday, China's official Xinhua News Agency said. It did not elaborate.
Its national airline, Air China, has canceled some flights to the North Korean capital, Pyongyang, due to poor demand but it has not suspended all flights there, it said on Friday.
China banned imports of North Korean coal on Feb. 26, cutting off its most important export. China's customs department issued an order on April 7 telling traders to return North Korean coal cargoes, said trading sources with knowledge of the order.
Saturday's parade combined with Sunday's failed missile launch made a sixth nuclear test increasingly likely, and if one was carried out, China would be compelled to support new sanctions against North Korea, the Global Times, an influential tabloid published by China's official Communist Party paper, the People's Daily, said in an editorial.
"Beijing should make clear to Pyongyang through diplomatic channels: if the DPRK in spite of the opposition of the international community (carry out a sixth nuclear test), China should cut off the vast majority of their oil supply and China should support the Security Council to pass new sanctions including this measure," the paper said, referring to North Korea by its official title, the Democratic People's Republic of Korea.
Worry about North Korea has led to a deterioration of ties between China and South Korea because China objects to the deployment of a U.S. Terminal High Altitude Area Defense (THAAD) anti-missile system in the South. The installation has begun but some opposition politicians have raised questions about it.
'It's moving. There are still some things to work out ... as in any government decision it may slip a couple of weeks or months," the U.S. adviser said of THAAD, whose powerful radar China fears could penetrate its territory.
'It's moving but candidly until they get a president ... It should be a decision for the next president.'
The South's presidential election is on May 9.
The adviser said there were 'a number of steps' that were discussed in Mar-a-Lago, Florida, between Chinese President Xi Jinping and Trump.
'We've seen the Chinese already take some initial steps toward that,' the official said, citing the turning back of the coal ships. 'Many steps still to take, but I think it's a good first step.'
Impoverished North Korea and the rich, democratic South are technically still at war because their 1950-53 conflict ended in a truce, not a peace treaty.
In Pyongyang, there was a festive atmosphere at a flower show, with families out, taking pictures with North Korean-made smart phones. There was no mention of the test failure on the KCNA state news agency.
Company worker Rim Chung Ryol, 30, said he had not heard of the test.
'If it is a failure, then failure is the mother of success,' he told Reuters.
Factory worker Ri Gul Chol, 37, also had not heard about the missile test.
'But whatever Kim Jong Un decides and instructs will succeed and all the citizens will support him,' he said, referring to the North's young leader.
