A U.S. initiative to spend hundreds of millions of dollars on construction projects in Afghanistan, originally pitched as a vital tool in the military campaign against the Taliban, is running so far behind schedule that it will not yield benefits until most U.S. combat forces have departed the country, according to a government inspection report to be released today.

The report, by the special inspector general for Afghanistan reconstruction, also concludes that the Afghan government will not have the money or skill to maintain many of the projects, creating an “expectations gap” among the population that could harm overall stabilization.

“Implementing projects that the Afghan government is unable to sustain may be counterproductive” to the U.S. counterinsurgency mission, the inspector general wrote. “If goals are set and not achieved, both the U.S. and Afghan governments can lose the populace’s support.”

The study calls into question a fundamental premise of the U.S. strategy to counter the Taliban insurgency — that expensive new roads and power plants can be funded and constructed quickly enough to help turn the tide of war — and it poses a sobering, counterintuitive question for policymakers in Washington: whether the massive influx of American spending in Afghanistan is actually making problems worse.

In a written response to the report, the U.S. Embassy in Kabul said it was “speculative” for the inspector general to conclude that some of the projects would have adverse effects. The top Pentagon official responsible for Afghanistan called the report premature and insisted that the announcement of the projects, even though they have not been completed, has generated goodwill and excitement among the Afghan people.