(KCTV/CNN) - North Korea has taken a major step forward in realizing its goal of becoming a nuclear power, according to the Washington Post.
The assessment concludes Pyongyang has developed a nuclear warhead capable of fitting inside its missiles.
The report came just hours after North Korea threatened "physical action" in response to punitive sanctions unanimously passed by the United Nations Security Council over the weekend.
The sanctions were in response to Pyongyang's two intercontinental ballistic missile tests in July.
The Washington Post story said that it is not known whether North Korea has successfully tested the smaller warhead design.
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