A new U.S. intelligence assessment says for the first time that North Korea may have developed a nuclear device small enough to mount on a ballistic missile, but said such a weapon’s “reliability would be low.”

In a seven-page, classified assessment by the Defense Intelligence Agency, a branch of the Pentagon, analysts appeared to upgrade U.S. estimates of North Korea’s nuclear weapons abilities.

Previously, experts didn’t think Pyongyang had the expertise to build a warhead small enough to affix to a missile.

The new assessment was divulged Thursday at a hearing of the House Armed Services Committee. Rep. Doug Lamborn (R., Colo.) referred to what he said was a classified report that had unclassified conclusions.

‘”DIA assesses with moderate confidence the North currently has nuclear weapons capable of delivery by ballistic missiles,”‘ the conclusion said, according to Mr. Lamborn. ‘”However, the reliability will be low.”‘

Defense officials would not confirm the finding and DIA officials would not comment later Thursday.