(CNN) - The chairman of the Joint Chiefs of Staff described the behavior of North Korea as "belligerent" on Sunday, following a report that the country is stepping up its nuclear program.
"It confirms or validates the concern we've had for years about their enriching uranium which they've denied routinely," Adm. Mike Mullen said on CNN's "State of the Union." "All of this is consistent with belligerent behavior, the kind of instability creation in a part of the world that is very dangerous."
The criticism follows a report from an American nuclear scientist who recently visited North Korea and was told the country is producing low-enriched uranium for a new reactor.
Mullen, the top U.S. military officer, said North Korea's actions violate United Nations Security Council resolutions.
"We've worked hard with other countries to bring pressure on them and to have them comply," Mullen told Candy Crowley, CNN's Chief Political Correspondent. "They're a country that routinely we are unable to believe that they would do what they say."
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