WASHINGTON -- A new assessment by the Pentagon's intelligence arm has concluded for the first time, with "moderate confidence," that North Korea has learned how to make a nuclear weapon small enough to be delivered by a ballistic missile.
The assessment by the Defense Intelligence Agency, which has been distributed to senior Obama administration officials and members of Congress, cautions that the weapon's "reliability will be low," apparently a reference to the North's difficulty in developing accurate missiles or, perhaps, to the huge technical challenges of designing a warhead that can survive the rigors of flight and detonate on a specific target.
The existence of the assessment was disclosed Thursday by Rep. Doug Lamborn, R-Colo., three hours into a budget hearing of the House Armed Services Committee with Defense Secretary Chuck Hagel and the chairman of the Joint Chiefs of Staff, Gen. Martin Dempsey. Gen. Dempsey declined to comment on the assessment because of classification issues.
Thursday evening, however, Pentagon press secretary George Little issued a statement that sought to qualify the conclusion of the Defense Intelligence Agency, which has primary responsibility for monitoring the missile capabilities of adversary nations, but which a decade ago was among those that argued most vociferously -- and incorrectly -- that Iraq had nuclear weapons.
"It would be inaccurate to suggest that the North Korean regime has fully tested, developed or demonstrated the kinds of nuclear capabilities referenced in the passage," Mr. Little said. "The United States continues to closely monitor the North Korean nuclear program and calls upon North Korea to honor its international obligations."
Nonetheless, outside experts said the report's conclusions could help explain why Mr. Hagel has announced in recent weeks that the Pentagon was bolstering long-range antimissile defenses in Alaska and California, designed to protect the West Coast, and rushing another anti-missile system, originally not intended for deployment until 2015, to Guam.
The disclosure of the Defense Intelligence Agency's assessment came the same day that the director of national intelligence, James Clapper, sought to tamp down fears that North Korean rhetoric could lead to an armed clash with the United States, South Korea and regional allies.
Mr. Clapper told a House Intelligence Committee hearing that, in his experience, two other confrontations with the North -- the 1968 seizure of the Navy spy ship Pueblo and the 1976 death of two U.S. soldiers in a tree-cutting episode in a border area -- stoked much greater tensions between the two nations.
Also Thursday, a high South Korean official called for dialogue with North Korea. The statement by the South Korean official, Unification Minister Ryoo Kihl-jae, was televised nationally and represented a considerable softening in tone by President Park Geun-hye's government.
U.S. Secretary of State John Kerry, meanwhile, was scheduled to arrive today in Seoul and to travel to China and Japan after that. He has two principal goals on the last leg of a six-nation trip: to encourage China to use its influence to persuade North Korea to abandon its nuclear weapons program and to reassure South Korea and Japan that the United States remains committed to their defense.
The Defense Intelligence Agency report last month was titled "Dynamic Threat Assessment 8099: North Korea Nuclear Weapons Program." Its executive summary reads: "DIA assesses with moderate confidence the North currently has nuclear weapons capable of delivery by ballistic missiles; however, the reliability will be low."
The material Mr. Lamborn quoted during the hearing was unclassified, his spokeswoman, Catherine Mortensen, said afterward. Pentagon officials later said that while the report remained classified, the one-paragraph finding had been declassified but not released. Republicans in Congress have led efforts to increase money for missile defense, and Mr. Lamborn has been critical of the Obama administration for failing to fund it adequately.
North Korea has conducted three nuclear tests, including one this year, and shot a ballistic missile as far as the Philippines in December. U.S. and South Korean intelligence agencies believe that another test -- perhaps of a midrange missile called the Musudan that can reach Japan, South Korea and almost as far as Guam -- may be conducted in coming days to celebrate the birth of Kim Il Sung, the country's founder.
At the Pentagon, there is particular concern about another missile, yet untested, called the KN-08, which may have significantly longer range.
"North Korea has already demonstrated capabilities that threaten the United States and the security environment in East Asia," Mr. Clapper told the House Intelligence Committee.