After supervising the test launch of a medium long-range strategic ballistic missile, North Korea leader Kim Jong-un says the country came to possess the ability to attack US interests in the Pacific, official media reported.
"We have the sure capability to attack in an overall and practical way the Americans in the Pacific operation theatre," Mr Kim was quoted as saying.
South Korean and US military officials reported on Wednesday that the North launched two intermediate-range Musudan missiles.
The first of the two was considered a failure, but the second flew 400 kilometres into the Sea of Japan.
North Korea's KCNA news agency said the test-fire was successful without any impact to the security of neighbouring countries.
Mr Kim, who personally monitored Wednesday's Musudan test, said it was a "great event" that significantly bolstered the North's pre-emptive nuclear attack capability.
KCNA said the missile had been fired at a high angle to simulate its full range and had reached a maximum height of more than 1,400 kilometres.
"It provided a sure sci-tech guarantee for developing the system of strategic weapons," the agency said.
"The test-fire was successfully conducted without giving any slightest effect to the security of surrounding countries."
The Musudan has an estimated range of anywhere between 2,500 and 4,000 kilometres.
The lower range covers the whole of South Korea and Japan, while the upper range would include US military bases on Guam.
After four failed Musudan launches earlier this year, a successful test marked a major step forward for a weapons program that ultimately aspires to develop a proven nuclear strike capability against the US mainland.
The North is believed to have up to 30 Musudan missiles, according to South Korean media, which officials said were first deployed around 2007, although the North had never attempted to test-fire them until April.
Reuters/AFP