North Korea test-fired a missile that failed immediately after launch early on Thursday, the US and South Korean militaries said, hours after the two countries agreed to step up efforts to counter the North's nuclear and missile threats.
The missile, believed to be an intermediate-range Musudan, was launched from the western city of Kusong, from where the isolated state had attempted and failed to launch the same type of missile on Saturday, the US Strategic Command and South Korea's Office of the Joint Chiefs of Staff said.
The launch comes after the United States and South Korea agreed in Washington on Wednesday to bolster military and diplomatic efforts to counter the North's nuclear and missile programs, which it is pursuing in defiance of UN Security Council resolutions.
After a meeting with South Korea's Defense Minister Han Min-koo on Thursday, U.S. Defense Secretary Ash Carter said such launches threatened the stability of the Korean peninsula and the broader Asia-Pacific region.
"We strongly condemn last night's attempt, that even in failing, violated several U.N. Security Council resolutions," he said at a news conference.
"This latest provocation only strengthens our resolve to work together with our (South Korean) allies to maintain stability on the peninsula."
The failed missile launch was the eighth attempt in seven months by the North to launch a weapon with a design range of 3,000 km (1,800 miles) that can be fired from road mobile launchers, the U.S. and South Korean militaries said.
Han said North Korea was conducting its missile launches for "political purposes" and was showing its limitations through the failures.
News of the North's latest ballistic missile launch came during the third and final U.S. presidential debate, in which Republican candidate Donald Trump and his Democratic rival, Hillary Clinton, exchanged sharply contrasting views on US alliances in Asia.
Trump said US defence treaties around the world, including with South Korea, had to be renegotiated because "we're being ripped off by everybody in the world."
Clinton said Trump wanted to tear up alliances that keep nuclear proliferation in check, relationships that she believed make the world and the United States safer.
Japan condemned the North Korean launch and said it would make a formal protest through its embassy in Beijing.
North Korea has been pursuing its nuclear and missile programs at an unprecedented pace this year.
In June, it launched a Musudan missile that flew about 400 km (250 miles), more than half the distance to Japan, a flight that was considered a success by officials and experts in South Korea and the United States.
North Korea said on Thursday that it would continue to launch satellites despite its rival South's objections, in a statement by its space agency carried by official media.
Pyongyang says it has a sovereign right to pursue a space program by launching rockets carrying satellites, most recently in February, although Washington and Seoul worry that such launches are long-range missile tests in disguise.
US Secretary of State John Kerry, speaking before the failed missile launch, said the United States would do "whatever is necessary" to defend itself, South Korea and other allies against North Korea.
Kerry and Carter reaffirmed that any attack by North Korea would be defeated, and any use of nuclear weapons "met with an effective and overwhelming response," a joint statement said.
As part of the military effort, Kerry said the United States would deploy the Terminal High Altitude Area Defence anti-missile system to South Korea "as soon as possible."
China strongly opposes deployment of the US system, saying it would impinge on its own strategic deterrence.
South Korean Foreign Minister Yun Byung-se, also speaking in Washington on Wednesday, said North Korea was nearing the "final stage of nuclear weaponisation" and the allies would mobilize "all tools in the toolkit" to defend themselves.
A US aerospace expert, John Schilling, said this week in a report on the 38 North project that despite the missile launch failures, the pace of testing could enable the North to put the Musudan missile into operational service sometime next year.
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