Washington ? A top Senate Democrat demanded Friday that the Bush administration explain the intelligence it received on North Korea’s nuclear weapons program after testimony this week suggested uncertainty about whether the communist regime has acquired the capacity to produce highly enriched uranium.

President Bush has said repeatedly that North Korea has been producing highly enriched uranium, which is used to produce nuclear bombs.

Sen. Carl Levin, D-Mich., made the request after testimony before his Senate Armed Services Committee revealed that U.S. intelligence agencies had only “midlevel” confidence that North Korea was secretly pursuing a uranium enrichment effort in addition to a publicly known plutonium program. Both enriched uranium and plutonium can be used to make nuclear weapons.

The assessment appeared to mark a shift backward from earlier judgments in which the intelligence community said it had “high confidence” that North Korea was building an industrial-scale uranium enrichment program.