In response, Dempsey said the extent of North Korean progress on designing a nuclear weapon small enough to operate as a missile warhead was a classified matter. But he did not rule out that the North has achieved the capability revealed in the DIA report.
"They have conducted two nuclear tests," Dempsey told a Pentagon news conference. "They have conducted several successful ballistic missile launches. And in the absence of concrete evidence to the contrary, we have to assume the worst case, and that's why we're postured as we are today." He was referring to recent moves by the U.S. to increase its missile defense capabilities in the Pacific.
At the same House hearing where Lamborn revealed the DIA conclusion, Defense Secretary Chuck Hagel was asked a different version of the same question: Does North Korea have the capability to strike U.S. territory with a nuclear weapon? Hagel said the answer is no.
"Now does that mean that they won't have it or they can't have it or they're not working on it?" Hagel added. "No. That's why this is a very dangerous situation."
"Now is the time for North Korea to end the belligerent approach they have taken and to try to lower temperatures," Obama said in his first public comments since Pyongyang threatened the United States and its allies in East Asia with nuclear attack.
Obama, speaking from the Oval Office, said he preferred to see the tensions on the peninsula resolved through diplomatic means, but added that "the United States will take all necessary steps to protect its people."
The North on Thursday delivered a fresh round of war rhetoric with claims it has "powerful striking means" on standby, the latest in a torrent of warlike threats seen by outsiders as an effort to scare and pressure South Korea and the U.S. into changing their North Korea policies.
Lamborn is a member of the Strategic Forces subcommittee of the Armed Services panel, which oversees ballistic missiles. A former state legislator who was elected to the House in 2006, was a member of the Tea Party caucus and belongs to the Republican Study Committee, the caucus of House conservatives
At a separate hearing Thursday, U.S. officials offered their assessment of the North Korean leader, who is a grandson of the country's founder, Kim Il Sung.
Clapper told the House Intelligence Committee that he thinks Kim, who took control after his father, Kim Jong Il, died in 2011, is trying to show the U.S., the world and his own people that he is "firmly in control in North Korea," while attempting to maneuver the international community into concessions in future negotiations.
"I don't think ... he has much of an endgame other than to somehow elicit recognition" and to turn the nuclear threat into "negotiation and to accommodation and presumably for aid," Clapper said.
Clapper said that the intelligence community believes the North would use nuclear weapons only to preserve the Kim regime but that analysts do not know how the regime defines that.
Secretary of State John Kerry was headed Thursday to East Asia, where he planned talks with officials in Seoul, Beijing and Tokyo about North Korea.
Associated Press writers Kimberly Dozier, Sagar Meghani and Donna Cassata contributed to this report.
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