(Alex Wong — Getty Images)

Secretary of State Hillary Rodham Clinton on Thursday told lawmakers that “we should build on our momentum, not undercut our progress” in Pakistan and Afghanistan, part of a bid to stave off Congress’s growing frustration over developments in the region.

“Working with our Afghan and Pakistani partners is not always easy, but these relationships are advancing America’s national security interests. And walking away would undermine those interests,” Clinton said.

The administration, she added, needs Congress as a full partner in the strategy. “This strategy requires resources,” Clinton told the House Foreign Affairs Committee. “I can’t sugarcoat that fact.”

Obama administration officials have been attempting a delicate balancing act in the region, on the one hand trying to keep Pakistan close and on the other insisting ever more vigorously that it crack down on militant leaders launching attacks in Afghanistan. Last week, while traveling to the region with a high-powered delegation of U.S. officials, Clinton warned the Pakistanis that they would have to pay a “very big price” if they did not take action against militants.

In Washington, lawmakers have grown increasingly skeptical about Pakistan’s commitment. Meanwhile, Afghan President Hamid Karzai’s remark over the weekend that he would side with Pakistan in a conflict with the United States has renewed concerns about his reliability as a U.S. ally.

“Now more than ever, President Karzai’s insult to America tells me that it’s time for our country to stop pouring our limited taxpayer dollars and losing precious American lives in a country where we aren’t even welcome — and even worse, where they have the gall to threaten to side against us,” Sen. Joe Manchin (D-W.Va.), a member of the Foreign Relations Committee, said.

In her remarks Thursday, Clinton emphasized the military progress the United States and its allies have made in Afghanistan, as well as the killing of Osama bin Laden and other top al-Qaeda leaders. She also acknowledged lawmakers’ concerns but said, as she has before, that there is no better alternative to sustaining U.S. efforts.

“America paid a heavy price for disengaging after the Soviets left in 1989. We cannot afford to make that mistake again,” she said. “We have to be smart and strategic. And we have to work together to protect our interests.”