The verdict isn't yet in as to whether Pakistan is a reliable ally in the United States's war in Afghanistan, the chairman of the Senate Armed Services Committee said Tuesday.

"The evidence is mixed as to whether or not the government in Pakistan is going to take on the religious extremists," Sen. Carl LevinCarl Milton LevinHow House Republicans scrambled the Russia probe Congress dangerously wields its oversight power in Russia probe The Hill's Morning Report — Sponsored by CVS Health — Trump’s love-hate relationship with the Senate MORE (D-Mich.) told National Public Radio (NPR).

"The border, particularly down in the south, between Pakistan and Afghanistan, is wide open now," said Levin, one of the top foreign policy voices in the Senate. "Extremists are flowing across that border into Afghanistan; Pakistan has not done anything to stop them."

Levin seemed to express skepticism that additional aid for Pakistan could produce a more hospitable situation on the ground for U.S. troops in neighboring Afghanistan.

"Any money which goes in to support the Pakistani army or the other parts of their security forces will not work unless they themselves are motivated to take on the Taliban," he said. "As far as the economic aid is concerned, we've provided economic aid before, and if you can show that it will be effective, I'm willing to consider that."

Levin added: "We can't buy their support. It's got to be a Pakistani goal to rid themselves of their own religious fanatics."

Listen to the audio of the interview here.