WASHINGTON — The Trump administration is urging US-backed Afghan troops to retreat from sparsely populated areas of the country, officials said, all but ensuring the Taliban will remain in control of vast stretches of the country.

The approach is outlined in a previously undisclosed part of the war strategy that President Trump announced last year, according to three officials who described the documents to The New York Times on the condition of anonymity.

It is meant to protect military forces from attacks at isolated and vulnerable outposts, and focuses on protecting cities such as Kabul, the capital, and other population centers.

The withdrawal resembles strategies embraced by both the Bush and Obama administrations that have started and sputtered over the nearly 17-year war.

It will effectively ensure that the Taliban and other insurgent groups will hold on to territory they have seized, leaving the government in Kabul to safeguard the capital and cities such as Kandahar, Kunduz, Mazar-e-Sharif, and Jalalabad.

The retreat to the cities is a searing acknowledgment that the US-installed government in Afghanistan remains unable to lead and protect the country’s sprawling rural population.

Over the years, as waves of US and NATO troops have come and left in repeated cycles, the government has slowly retrenched and ceded chunks of territory to the Taliban, cleaving Afghanistan into disparate parts and ensuring a conflict with no end in sight.

In a reversal of a long-standing policy, US diplomats held face-to-face talks with Taliban representatives in Qatar a week ago without Afghan government officials present, two senior Taliban officials said Saturday.

The State Department did not immediately respond to a request for comment Saturday. But the department has not denied that its diplomats had taken part in such talks — a significant shift in American strategy toward the Taliban in Afghanistan.

The Afghan president’s office said Saturday that it welcomed any support for peace efforts.

The talks took place in Doha, where the Taliban have long maintained an informal “political office’’ for the purpose of restarting the long-dormant peace process.

They involved several members of the Taliban political commission and Alice Wells, the State Department’s senior South Asia diplomat, as well as other unidentified US diplomats, according to the two Taliban officials.

The Taliban officials spoke on condition of anonymity because of the diplomatic sensitivities around the talks.

When he announced his new war strategy last year, Trump declared that Taliban and Islamic State insurgents in Afghanistan “need to know they have nowhere to hide, that no place is beyond the reach of American might and American arms.’’

After the declared end of combat operations in 2014, most US troops withdrew to major population areas in the country, leaving Afghan forces to defend remote outposts. Many of those bases fell in the following months.

During a news conference last month in Brussels, Gen. John W. Nicholson Jr., commander of the U.S.-led coalition in Afghanistan, said remote outposts were being overrun by the Taliban, which was seizing local forces’ vehicles and equipment.

“There is a tension there between what is the best tactic militarily and what are the needs of the society,’’ Nicholson said.

The strategy depends on the Afghan government’s willingness to pull back its own forces. A Defense Department official said some Afghan commanders have resisted the US effort to do so, fearing local populations would feel betrayed.

“Abandoning people into a situation where there is no respect for them is a violation of human rights,’’ said Mohammad Karim Attal, a member of the Helmand Provincial Council. “This might be the weakest point of the government that does not provide security and access to their people’s problems.’’

Just over one-quarter of Afghanistan’s population lives in urban areas, according to CIA estimates; Kabul is the largest city, with more than 4 million residents. Most Afghans live and farm across vast rural hinterlands.

Of Afghanistan’s 407 districts, the government either controls or heavily influences 229 to the Taliban’s 59. The remaining 119 districts are considered contested, according to the Office of the Special Inspector General for Afghanistan Reconstruction.

Hamdullah Mohib, the Afghan ambassador to the United States, disputed that the American and Afghan forces were leaving rural areas and essentially surrendering them to the Taliban.

The intent was not to withdraw, Mohib said in an e-mail, but to first secure the urban areas to allow security forces to later focus on rural areas.

Hundreds of Afghan troops are being killed and wounded nearly every week — many in Taliban attacks on isolated checkpoints.

Over the past year alone, the number of Afghan soldiers, police, pilots, and other security forces dropped by about 5 percent, or 18,000 fewer people, according to the inspector general’s office.

“This brings a very serious tension — when you’ve had significant loss of life, and blood and treasure,’’ said Paul Eaton, a retired two-star Army general who helped train Iraqi forces in the year after the 2003 invasion of Baghdad. “But it is time to say that we need a political outcome.’’

Eaton said the plan to prod the Afghan military to abandon the unpopulated areas and retrench to major cities is “a rational approach to secure the cities, and provide the Afghanistan government the political opportunity to work with the Taliban.’’

The strategy for retreat borrows heavily from President Obama’s military blueprint in Afghanistan after he began withdrawing troops from front lines in 2014.

Should Afghan troops pull back now, defending remote pockets of the country would mostly be left to the local police, which are more poorly trained than the military and far more vulnerable to Taliban violence.

In some areas, police officers have cut deals with the Taliban to protect themselves from attacks.