By Phil Stewart

KABUL (Reuters) -The U.S. general leading the war in Afghanistan, Austin Miller, relinquished command on Monday at a ceremony in Kabul, in what was a symbolic end to America’s longest conflict even as Taliban insurgents gain momentum across the country.

Miller, America’s last four-star commander to serve on the ground in Afghanistan, stepped down ahead of a formal end to the U.S. military mission there on Aug. 31, a date set by President Joe Biden as he looks to extricate the country from the two-decade-old war.

Addressing a small gathering outside his military headquarters in Kabul, Miller vowed to remember the lives lost in the fighting and called on the Taliban to halt a wave of violent attacks that have given them control of more territory than at any time since the conflict began.

“What I tell the Taliban is they’re responsible too. The violence that’s going on is against the will of the Afghan people, and it needs to stop,” Miller said. While the ceremony may offer some sense of closure for U.S. veterans who served in Afghanistan, it’s unclear whether it will succeed in reassuring the Western-backed Afghan government as the Taliban press ground offensives.

U.S. Marine General Kenneth McKenzie, whose Florida-based Central Command oversees U.S. forces in hot-spots including Afghanistan, Iraq and Syria, flew into Kabul to underscore America’s future assistance to Afghan security forces.

“You can count on our support in the dangerous and difficult days ahead. We will be with you,” McKenzie said in his address.

Speaking separately to a small group of reporters, McKenzie cautioned that the Taliban, in his view, were seeking “a military solution” to a war that the United States has unsuccessfully tried to end with a peace agreement between the Taliban and Afghan President Ashraf Ghani’s government.

He said provincial capitals were at risk but noted that the U.S.-backed Afghan security forces “are determined to fight very hard for those provincial capitals.”

McKenzie will be able to authorize U.S. air strikes against the Taliban through Aug. 31 in support of Ghani’s Western-backed government.

But after that, the Marine general said when it came to U.S. strikes in Afghanistan, his focus will shift squarely to counter-terrorism operations against al Qaeda and Islamic State.

INTELLIGENCE NETWORK

Gathering enough intelligence on the ground to prevent another Sept. 11-style attack could become increasingly challenging, as America’s intelligence network weakens with the U.S. withdrawal and as Afghan troops lose territory.

U.S. Representative Elissa Slotkin, a Democrat and former senior Pentagon official, said many lawmakers were still looking for answers from the Biden administration about how the U.S. will be able to detect a future al Qaeda plot against the United States.

“I don’t need them to tell the entire world what our day-after plan is. But I think it’s important that they let us know some of the details on a private basis,” Slotkin said.

U.S. officials do not believe the Taliban could be relied upon to prevent al Qaeda from again plotting attacks against the United States from Afghan soil.

The United Nations said in a report in January there were as many as 500 al Qaeda fighters in Afghanistan and that the Taliban maintained a close relationship with the Islamist extremist group.

LONGEST-SERVING GENERAL

As he steps down, Miller, 60, has spent longer on the ground than any of the previous generals to command the war.

He had a close call in 2018 when a rogue Afghan bodyguard in Kandahar province opened fire and killed a powerful Afghan police chief standing near Miller. A U.S. brigadier general was wounded, as were other Americans, but Miller emerged unscathed.

After Miller leaves the post, the Pentagon has engineered a transition that will allow a series of generals to carry on with supporting Afghan security forces, mostly from overseas.

Beyond McKenzie’s over watch from Florida, a Qatar-based brigadier general, Curtis Buzzard, will focus on administering funding support for the Afghan security forces – including aircraft maintenance support.

In Kabul, Navy Rear Admiral Peter Vasely will lead a newly created U.S. Forces Afghanistan-Forward, focusing on protecting the U.S. embassy and the airport.

Vasely, as a two-star admiral, is higher ranked than usual for a U.S. embassy-based post. But a U.S. defense official added that Afghanistan was a “very unique situation.”

“There’s no comparable diplomatic security situation in the world with what we’re going to establish,” the official said, speaking on condition of anonymity.

Still, what happens next in Afghanistan appears to be increasingly out of America’s control.

Biden acknowledged on Thursday that Afghanistan’s future was far from certain but said the Afghan people must decide their own fate.

“I will not send another generation of Americans to war in Afghanistan with no reasonable expectation of achieving a different outcome,” he said.

About 2,400 U.S. service members have been killed in America’s longest war – and many thousands wounded.

(Reporting by Phil StewartEditing by Robert Birsel and Paul Simao)