In private, top Afghan and American officials have begun to voice increasingly grim assessments of the resurgent Taliban threat, most notably in a previously undisclosed transcript of a late-October meeting of the Afghan National Security Council.

“We have not met the people’s expectations. We haven’t delivered,” Abdullah Abdullah, the country’s chief executive, told the high-level gathering. “Our forces lack discipline. They lack rotation opportunities. We haven’t taken care of our own policemen and soldiers. They continue to absorb enormous casualties.”

With control of — or a significant presence in — roughly 30 percent of districts across the nation, according to Western and Afghan officials, the Taliban now holds more territory than in any year since 2001, when the puritanical Islamists were ousted from power after the 9/11 attacks. For now, the top American and Afghan priority is preventing Helmand, largely secured by U.S. Marines and British forces in 2012, from again falling to the insurgency.

As of last month, about 7,000 members of the Afghan security forces had been killed this year, with 12,000 injured, a 26 percent increase over the total number of dead and wounded in all of 2014, said a Western official with access to the most recent NATO statistics.