President Donald Trump has warned Kim Jong-un not to void his special relationship with the US after North Korea carried out a "very important test" at its long-range rocket launch site on the weekend.
The location was reportedly rebuilt after it was partially dismantled when the two nations entered denuclearisation talks last year.
The announcement comes amid dimming prospects for a resumption of negotiations, with the North warning it would seek "a new way" if it fails to get major US concessions by year's end.
North Korea has said its resumption of nuclear and long-range missile tests depends on the US.
North Korea has said its resumption of nuclear and long-range missile tests depends on the US.
Trump tweeted: "Kim Jong Un is too smart and has far too much to lose, everything actually, if he acts in a hostile way. He signed a strong Denuclearization Agreement with me in Singapore. He does not want to void his special relationship with the President of the United States."
A senior Trump administration official told NBC News Sunday: "We have seen the reports of a test and are coordinating closely with allies and partners."
On Saturday, President Donald Trump and South Korean President Moon Jae-in discussed developments related to North Korea and the two leaders committed to continue close communication, the White House said in a statement.
President Donald Trump has warned Kim Jong-un not to void his special relationship with the US after North Korea carried out a "very important test" at its long-range rocket launch site on the weekend.
Moon's office also released a similar statement, saying the two leaders had a 30-minute phone conversation at Trump's request.
Saturday's test at the Sohae Satellite Launching Ground will have "an important effect on changing the strategic position of (North Korea) once again in the near future," an unidentified spokesman from the North's Academy of National Defence Science said in a statement, according to the official Korean Central News Agency.
He said the defence academy submitted the test results to the Central Committee of the ruling Workers' Party. The North said last week that the Central Committee will hold a meeting in late December to discuss unspecified "crucial issues" in line with "the changed situation at home and abroad."
North Korea didn't say what the test included.
Analyst Kim Dong-yub at Seoul's Institute for Far Eastern Studies said that North Korea likely tested for the first time a solid-fuel engine for an intercontinental ballistic missile. The use of solid fuel increases a weapon's mobility.
Saturday's test "is meant to improve military capabilities and to shore up domestic pride and legitimacy," said Leif-Eric Easley, a professor at Ewha University in Seoul.
"With the activity at Sohae, Pyongyang is also trying to raise international concerns that it may intensify provocations and walk away from denuclearization talks next year."
The Sohae launching center in Tongchang-ri, a seaside region in western North Korea, is where the North has carried out banned satellite launches in recent years, resulting in worldwide condemnation and U.N. sanctions over claims that they were disguised tests of long-range missile technology.
North Korea has said its satellite launches are part of its peaceful space development program.
