WASHINGTON — America should rethink a multimillion-dollar program aimed at training and equipping a paramilitary force in Pakistan unless the country does more to keep terrorists from crossing the Afghan border, a Democratic senator said yesterday.

The chairman of the Senate Armed Services Committee, Senator Levin, told reporters after a three-day trip to the region that American officials have little confidence that segments of the Pakistan government, particularly its army, are working actively to stop the flow of Taliban fighters and weapons into Afghanistan. In some cases, these groups might even be providing support to terrorists, he said.

“If that’s our intelligence assessment, then there’s a real question as to whether or not we should be putting money into strengthening the Frontier Corps on the Pakistan side,” Mr. Levin, Democrat of Michigan, said in a conference call from Qatar.

Mr. Levin is among a growing chorus of Democrats questioning the more than $10 billion in U.S. military and economic aid given to Pakistan to fight terrorism since the September 11, 2001, attacks on America. Last month, a report by the Government Accountability Office found that despite the money, terrorists are still operating freely along the Afghan border.