The Pentagon's intelligence arm has assessed with "moderate confidence" that North Korea has the ability to deliver a nuclear weapon with a ballistic missile though the reliability is believed to be "low."
Disclosed first by a congressman at a hearing on Thursday and then confirmed to CNN by the Defense Department, the assessment by the Defense Intelligence Agency (DIA) is the clearest acknowledgment yet by the United States about potential advances in North Korea's nuclear program.
The surprise development comes amid heightened tensions on the Korean Peninsula. North Korea has unleashed a torrent of dramatic threats against the United States and South Korea in recent weeks, including that of a possible nuclear strike.
The Obama administration calculates a test launch of mobile ballistic missiles could come at any time. But a senior administration official said there is no indication that missiles believed being readied for tests have been armed with any nuclear capability.
Rep. Doug Lamborn, R-Colorado, read from an unclassified version of the intelligence assessment at a House Armed Services Committee hearing.
"DIA assess with moderate confidence the North currently has nuclear weapons capable of delivery by ballistic missiles, however, the reliability will be low."
Pentagon spokesman George Little refused to comment in an interview with CNN's Jake Tapper, saying that while the conclusion was unclassified, "the underlying content is definitely classified."
Joint Chiefs Chairman Gen. Martin Dempsey, who was testifying before the House committee, appeared to be caught off guard when asked by Lamborn whether he agreed with the assessment.
"Well, I haven't seen it," Dempsey replied. "And you said it's not publicly released, so I -- I choose not to comment on it."
It is was not clear if other U.S. intelligence agencies, like the CIA, agree with the defense analysis.
Since December, North Korea has put a satellite in orbit atop a long-range rocket; conducted a nuclear bomb test, its third since 2006; and claimed to be prepared for pre-emptive nuclear attacks on the United States, though most analysts believe it does not yet have that capability.
Its most recent nuclear test, in February, resulted in tougher U.N. sanctions, which infuriated Pyongyang, prompting it to sharpen its threats.
Annual military exercises in South Korea by U.S. and South Korean troops, which often upset the North, have added to the tensions, especially when the United States drew attention to shows of strength such as a practice mission by B-2 stealth bombers.