WASHINGTON -- A former Republican senator who was once a cabinet choice for President Barack Obama is calling for a quicker withdrawal from Afghanistan, saying the country cannot continue to shoulder the economic and human burden.

"I don't think we can afford Afghanistan much longer," said former New Hampshire Sen. Judd Gregg, who retired in January, during an interview on MSNBC's "Morning Joe" on Monday. "The simple fact is that it's costing us. Good people are losing their lives there, and we're losing huge amount of resources there ... So I think we should have a timeframe for getting out of Afghanistan, and it should be shorter rather than longer."

When asked by panelist Willie Geist if he wished Obama would "set clear guidelines as to when this is going to end and what we're doing there" and whether he "finds some political courage among some of [his] former colleagues to start moving in that direction," Gregg replied, "I think we have to."

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Gregg originally supported the invasion of Afghanistan, and as recently as March 2009 -- shortly after he withdrew his name from consideration for Commerce Secretary -- said he backed Obama on foreign policy. "I'm perfectly happy to be supportive of the president when he's on the right track on places like Afghanistan and Iraq," said Gregg, who later became one of the administration's sharpest critics on government spending.

His comments on Monday come as Defense Secretary Robert Gates visits Afghanistan to meet with Afghan President Hamid Karzai. Gates said Monday that both the U.S. and Afghan governments agree U.S. forces should remain in Afghanistan even after 2014, which Obama has targeted as the end of combat operations.

"Obviously it would be a small fraction of the presence that we have today, but I think we're willing to do that," Gates said. "My sense is, they are interested in having us do that."

During the MSNBC interview, Gregg said that the focus should be on Pakistan -- and perhaps even India -- rather than Afghanistan, a sentiment shared by some current lawmakers. Sen. Chris Coons (D-Del.), who recently returned from a trip to the region and sits on the Senate Foreign Relations Committee, told reporters last month that the administration needed to focus more attention on Pakistan. "[O]ur biggest problem in Afghanistan is Pakistan," he said. Sen. Joe Manchin (D-W.V.), who was on the trip with Coons, has also expressed concerns about the cost: "When you look at all the financial challenges we have as a nation, are we really moving down the right path? How much more sacrifice from the United States will be needed?"

Gregg did not identify which of his former colleagues, if any, are shifting away from the Republican party line on Afghanistan. While a small group of GOP House members are working to explore alternatives, they have not yet been able to make significant inroads in getting other lawmakers to speak out publicly. In January, Senate Minority Leader Mitch McConnell (R-Ky.) said that "virtually" all GOP senators "support what the president's doing" on the war.