KABUL, Afghanistan — The commander of the U.S.-led mission in Afghanistan warned on Tuesday that the country could be on a path to chaotic civil war as American and other international troops prepare to leave in the coming weeks.

His assessment, in a rare news conference at the headquarters of U.S. and NATO command in Kabul, will likely be one of the last publicly delivered by an American four-star general in Afghanistan, where recent events have included a Taliban offensive that has seized around 100 district centers, left dozens of civilians wounded and killed, and displaced thousands more.

“Civil war is certainly a path that can be visualized if it continues on the trajectory it’s on,” the commander, Gen. Austin S. Miller, told reporters during the news conference. “That should be a concern for the world.”

With some intelligence estimates saying that the Afghan government could fall in six months to two years after a final American withdrawal, General Miller’s comments were a window into recent tension between the White House and the Pentagon.

For months, Pentagon leaders argued for some sort of lasting American military presence in Afghanistan, citing counterterrorism concerns and the need to provide a check on the Taliban’s advance. President Biden’s response, in April, was final: All American forces except for an embassy garrison will be gone by Sept. 11.

Speaking from a garden adjacent to the circle of flagpoles that once displayed the flags of the 36 countries that contributed to the U.S.-led NATO mission — now reduced to Turkey, Britain and the United States — General Miller said the troop withdrawal was reaching a point where he would soon end his command, which began in September 2018, and in turn, say goodbye to Afghanistan.

“From a military standpoint it’s going very well,” General Miller said of the U.S. withdrawal. He did not offer a timeline for when the withdrawal will be complete. The Taliban, for the most part, have not attacked U.S. or international forces as they have departed, instead focusing the brunt of the violence on the Afghanistan security forces and the civilians caught in the crossfire.

What U.S. forces remain are spread between Kabul and Bagram Air Base, the sprawling base that was once home to thousands of troops and contractors. Bagram is now the final gateway for moving out what troops and equipment remain in the country.

The NATO headquarters, soon to become part of the U.S. Embassy compound, was quiet Tuesday. The Georgian guards who had manned its perimeter were gone, replaced by U.S. Embassy security. The interior, a web of protective cement barriers, barracks and offices, felt much like an empty home.

Roughly 650 U.S. troops are expected to remain in the country to provide security for diplomats, American officials said last week.

The U.S. military inches closer to the exit, but it is still providing what support it can to the Afghan security forces — flying jets from the aircraft carrier Eisenhower, recently replaced by the Reagan, over Afghanistan to drop airstrikes on Taliban fighters as Afghan security have found themselves under siege.

But with much of the high-tech American communications equipment gone, in at least one instance those jets were unable to communicate properly to carry out an airstrike on Taliban positions and had to pass the attack off to an armed drone, said one military official, who spoke on the condition of anonymity to discuss sensitive matters. Currently much of the air support over Afghanistan has already been moved out of the country.

But what the Americans are doing in Afghanistan becomes less relevant by the day as their presence in the country shrinks, and with it their capacity to affect what happens on the battlefield.

The United States has spent billions of dollars propping up Afghan security forces, but it remains unresolved whether it will continue to provide those forces with air support after Sept. 11, when American troops are withdrawn.

The United States currently has “the ability to support Afghan security forces when attacked,” General Miller said. “That exists today, and I don’t want to speculate what that looks like in the future.”

U.S. airstrikes, targeting groups of Taliban fighters following their recent offensive in the country’s north, have drawn outrage from the Taliban but little else as their fighters continue to take territory daily. The insurgent group has taken dozens of districts in past weeks — sometimes through military means and at others by exploiting local divisions along with mediation with local officials.

Afghan forces have managed to retake several districts, but nothing on the scale of their insurgent foes.

“What we’re seeing is the rapid loss of district centers,” General Miller said, adding that he had passed his advice — to pull security forces back to defend key areas such as big cities — on to Afghan leaders.

This domino effect of falling districts has only served to demoralize the Afghan security forces, who have watched some of their comrades surrender, forfeiting their vehicles and equipment to an increasingly triumphant Taliban. In recent days, the fighting had reached roughly 60 miles away from Kabul, the country’s capital.

To bolster the depleted government forces, militias — some long on the government’s payroll — have gained new prominence, a distinct echo of the civil war in the 1990s when warlords and their fiefs of armed men harassed and taxed residents to the point where the Taliban’s rise was welcome in broad areas of the country. Both President Ashraf Ghani and his newly appointed defense minister have made comments that seemed to welcome the resurgence of such groups.

The militias’ efficacy on the battlefield is questionable, but the government will continue to back their rise because “it will bleed the Taliban by a thousand cuts,” said Ibraheem Bahiss, a consultant with International Crisis Group and independent research analyst.

The Biden administration has pledged to provide Mr. Ghani with financial support. That includes $266 million in humanitarian aid and $3.3 billion in security assistance, as well as three million doses of the Johnson & Johnson coronavirus vaccine and oxygen supplies.

Still, Mr. Biden’s message in his meetings with the Afghan leaders was clear: The U.S. military was leaving.

NATO and the U.S. military will also continue to assist the Afghan security forces with training and logistics from outside the country.

“Afghans are going to have to decide their future, what they want,” Mr. Biden said at the White House. “The senseless violence has to stop.”

But the violence is unlikely to come to a halt anytime soon. Peace talks in Doha between the Afghan government and the Taliban that began in September have all but stalled, and with the insurgents’ gains on the battlefield, the Taliban is increasingly likely to only settle for an outright military victory.

Speaking to reporters in Washington hours after General Miller’s remarks, the Pentagon spokesman, John F. Kirby, deflected questions on the precise timing of the final withdrawal of American forces — officials have previously said early to mid-July — and on how the Pentagon and Biden administration would mark that occasion.

No senior Pentagon officials are expected to visit Afghanistan as the last troops leave. And it is unclear what kind of official homecoming ceremonies — if any — the last returning troops and their commanders, including General Miller, will receive.

“We’re all mindful, all of us here, of the fact that this war is now two decades on, and is coming to a close, and of our responsibility to communicate the closure of that to you and to the American people and we will do that,” Mr. Kirby said.

“We will find a way to mark it officially,” he added, “and to state it unequivocally for the American people at the right time and in an appropriate way.”

Eric Schmitt reported from Washington.