WASHINGTON -- Frustrated American military officers and civilian officials working in Afghanistan are increasingly questioning the U.S. war strategy, with some arguing that U.S. lives and money are only propping up an Afghan government that will collapse once that support ends.

Those officers and officials have company in the American people. A new poll out this week shows record opposition to the war. Yet they have a prominent and powerful opponent: Gen. David Petraeus, who testified in two days of congressional hearings this week that significant progress is being made in Afghanistan.

After nine years of combat, at a cost of 1,422 Americans killed and 9,971 wounded and no clear end in sight, almost two-thirds of the American public -- 64 percent -- now believe the Afghan war is not worth fighting, according to a new Washington Post/ABC News poll. The poll, which documented the highest-ever opposition to the war, found that most support for President Barack Obama's war policies now come from Republicans.

Privately, even many of those working under Petraeus have expressed concern that without constant pressure by U.S. troops and a steady flow of taxpayer dollars, the gains they have made against the Taliban would quickly be lost.

Petraeus, the architect of the counterinsurgency strategy, said Tuesday that the "comprehensive'' military and civilian campaign now underway for more than a year has achieved "important, but hard-fought, progress,'' with "tough losses along the way.'' But he said the general trajectory has been "upward.''

The highly decorated four-star general credited with a successful counterinsurgency campaign in Iraq, Petraeus was given command of 150,000 U.S. and allied troops in Afghanistan last summer after the resignation of Gen. Stanley McChrystal. Petraeus told the Senate Armed Services Committee Tuesday that the war is going well enough so that he can begin to "thin out'' U.S. forces by July, as Obama has promised.

U.S. troops have seized key territory from the Taliban, killed or captured "numerous'' insurgent leaders and trained a growing Afghan security force, Petraeus said. Working with about 1,100 American civilian advisers and development officials, they have provided jobs and helped develop local government.

But he said the progress is "fragile and reversible,'' making it impossible for him to say how many troops could be brought home this summer.

"This is not a campaign where we take the hill, plant the flag and come home to a victory parade,'' Petraeus said. Preventing al Qaeda's return to sanctuary inside Afghanistan, he said, requires not just the purely military mission of protecting Afghans from the Taliban, but also helping Afghanistan "develop sufficient capabilities to secure and govern itself.''

For that kind of development work, separate from the cost of military operations, the State Department has requested an additional $2.2 billion for civilian work in Afghanistan for next year. Petraeus acknowledged that the future U.S. financial commitment for development of that kind will be "considerable.''

How well the money is spent, and what permanent effect it has, varies widely among Afghanistan's districts and villages. In places like Dand District, just south of the provincial capital city of Kandahar in southern Afghanistan, five years of military operations and development investment are paying off as local government begins to be able to act on its own in conjunction with a U.S. Army battalion.

But elsewhere, that kind of investment seems to have more tenuous effects. In the Nawa District in nearby Helmand Province, progress in both security and local government "is entirely dependent'' on a sustained flow of American money, according to Scott Dempsey, a former Marine who served there as a development officer in 2009 and 2010..

Nawa is often cited by Petraeus as a "proof of concept'' of his counterinsurgency strategy. For visiting journalists and politicians, he has showcased the combination of security, development and governance that he has insisted can transform a district from a Taliban safe haven into a secure, thriving and self-governing community.

More than 1,000 U.S. Marines thronged into Nawa in 2009 and quickly sent the Taliban fleeing. USAID poured in $25 million in development aid -- over $300 per resident. About half of the district's 20,000 working-age Afghans got U.S.-funded jobs, spurring at least a short-term economic boom, and the district market, once nearly abandoned, became a bustling center of commerce.

Among those who visited Nawa at the suggestion of the U.S. command was first-year Sen. Kelly Ayotte (R-N.H.). "I was impressed with the progress being made,'' Ayotte told Petraeus Tuesday. Speaking to the doubts about the effectiveness of the strategy, she added: "Sometimes the press focuses on the bad things, and the progress that is being made there is not reported on enough.''

But that's not what Dempsey observed during the nine months he served in Nawa. The bustling marketplace and charismatic district governor "masked the overriding long-term problem that the Afghan government's success was based almost entirely on American inputs,'' he wrote in an essay in Small Wars Journal, an online magazine devoted to counterinsurgency, or "COIN."

"Even the most basic degree of Afghan government-led stability will require a seemingly endless commitment to continue to fight and finance this effort,'' wrote Dempsey, who until last month worked on Afghanistan affairs at the U.S. Agency for International Development in Washington.

"Our current practice of COIN fails to understand that the only meaningful metric for success is a transfer of sustainable sovereignty to the institutions we can easily create -- but which the Afghans must learn to run,'' Dempsey went on. When the money inevitably runs out, he wrote, power will quickly shift to the Taliban and the drug lords.

Dempsey's misgivings about the strategy are echoed by other officers who declined to speak on the record. But they also spoke of their worry that the security gains their soldiers and Marines had made would eventually be lost to the Taliban because the local government was corrupt or inept or both. As Petraeus himself warned Congress, "If the Afghan government can't or doesn't provide those basic services, then there will be a reversion to the Taliban, however little the people have regard for them -- and they remember what it was like under the brutal rule of the Taliban.'' Petraeus argued that a substantial number of American troops will be needed well after this July, while the Afghan government, at the national and local levels, is prodded and encouraged and trained. While the Post-ABC poll found that nearly 80 percent of respondents wanted a "substantial'' withdrawal of troops this summer, Petraeus said many of those who are withdrawn from secure areas may be reassigned within Afghanistan rather than brought back home. "We should not rush to failure,'' Sen. John McCain (Ariz.), the ranking Republican on the armed services committee, said by way of agreement with Petraeus. "The next several months will be decisive'' as the Taliban attempt to surge back, he said. "We need to be exceedingly cautious about the withdrawal of U.S. forces this July.''

One alternative to the current strategy would be to refocus the military mission on partnership with Afghan security forces against the Taliban, allowing the force to be reduced to 25,000 to 35,000 troops. Under such a plan, U.S. and allied civilian assistance should be shifted away from the central government in Kabul to concentrate on local government, where most people receive direct services.

That kind of approach is detailed, among other places, in a recent report by the Center for a New American Security, a nonpartisan think tank in Washington.