North Korea has accused the US of threatening war by conducting a missile defence test and vowed to strengthen its self-defence in response.
The US was increasing tensions on the Korean peninsula with its test and by holding military drills with South Korea, a North Korean statement said.
Hours earlier, the US military said it had successfully intercepted a dummy long-range warhead over the Pacific.
In July, Pyongyang test-fired several missiles, raising regional tensions.
The US Missile Defence Agency (MDA) said a target missile launched from Alaska was successfully shot down by an interceptor sent up from California on Friday.
"What we did today is a huge step in terms of our systematic approach to continuing to field, continuing to deploy and continuing to develop a missile defence system for the US, for our allies, our friends, our deployed forces around the world," Lt Gen Henry Obering, the MDA's director, said.
Military drills
The test drew a quick and furious response from North Korea.
It "was aimed at attacking us and intercepting our missiles," said a statement from North Korea's Committee for the Peaceful Reunification of the Fatherland carried by the official KCNA news agency.
The US was "the main culprit" in bringing about the danger of war on the Korean peninsula, the statement said.
"It is a folly that the United States wields the truncheons of power in order to scare someone into submission...This only leads the army and the people to firm up their determination to build up our self-defensive military deterrence."
The North Korean statement also repeated its condemnation of the 10-day military exercise by US and South Korean forces which ended on Friday.
The drills are an annual event and the North usually issues a strongly-worded statement against them.
But this year, tensions are higher than normal amid international concern over North Korea's recent test-firing of a series of missiles and its continuing refusal to return to six-party talks on its nuclear ambitions.
July's test included the unsuccessful firing of a Taepodong-2, a new long-range multi-stage missile which is believed to have the capability of reaching Alaska and Hawaii.
'Waste of money'
The MDA said Friday's $85m test was an important exercise aimed at protecting the United States against a limited long-range ballistic missile attack.
"What we saw today was a very realistic trajectory for the threat, for the target, and a very realistic intercept altitude and intercept speeds," Gen Obering said.
The US missile defence system under development uses radar and satellites to detect enemy missile launches and to guide interceptors to their targets.
But it has a mixed record, with only five successful tests out of nine and critics say the system, whose budget has reportedly grown to $10bn (£5.25bn) a year, is a waste of money.
Another interceptor test will take place later this year or in early 2007, the MDA said.
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