On Friday morning, a Republican member of Congress said “demonstrated” was the crucial phrase: North Korea has never conducted a test of a warhead, showing that it could be precisely targeted or that it could survive the heat and forces of re-entry into the atmosphere. But he said that there is “a consensus building” among rival intelligence agencies that “If they are not there, they are close to there.” Differences among the assessments, he added, “are not huge.”

The last time the differences among intelligence agencies came into such sharp relief was 10 years ago this spring, when the Bush administration sought to explain why it had dismissed the dissenting opinions of parts of the intelligence community over Iraq’s nonconventional weapons.

The Defense Intelligence Agency’s conclusion was clearly an assessment that the Obama administration was not eager to share with the world. Officials said that at a moment when there were troubles with Iran and Syria, to say nothing of the rest of the Arab world, there was little desire to rekindle the North Korean crisis. That is especially true because North Korea has not demonstrated any capability to place its weapons on a missile, meaning that all the intelligence assessments were based on analysis, not discoveries.

But that effort came undone when a staff member on a House Armed Services subcommittee that oversees nuclear issues read a copy of the agency’s classified report, as part of his regular staff work, according to two people briefed on the matter who spoke on the condition of anonymity to describe the internal communications between Congress and the Pentagon.

The staff member noticed an important one-paragraph conclusion that was labeled “unclassified,” and went to the Defense Intelligence Agency’s legislative affairs liaison, who confirmed it. The staff member then alerted an influential member of the subcommittee, Representative Doug Lamborn, a fourth-term Republican of Colorado and a co-chairman of the House’s missile defense caucus, who decided to ask Defense Secretary Chuck Hagel and Gen. Martin E. Dempsey, the chairman of the Joint Chiefs of Staff, about the report’s conclusion at a budget hearing on Thursday. “It’s important to have all the facts on the table,” Mr. Lamborn said in a telephone interview Friday, adding that he had no misgivings about asking his question in a public hearing.

Republicans in Congress have led efforts to increase money for missile defense, and Mr. Lamborn said that he raised the issue largely because the Obama administration proposed this week in its annual budget submission to reduce financing for missile defenses by more than $500 million.

Given the agency’s responsibility for protecting American forces, it is not surprising that the Defense Intelligence Agency has been the most aggressive in arguing that North Korea is on the verge of marrying the products of its nuclear and missile programs. Two years ago, Lt. Gen. Ronald L. Burgess Jr., then the head of the agency, edged up to a similar conclusion, but with several caveats.