The Taliban claimed responsibility for an attack Monday on American troops that killed one US soldier and, according to the insurgents, wounded several more.
The killing is likely to have consequences for ongoing talks between the US and the Taliban. President Donald Trump in September declared negotiations "dead" after the Taliban killed a US soldier in a Kabul bombing.
Negotiations have since restarted in Doha, but were earlier this month put on a "pause" following yet another bombing, this time at the Bagram air base north of Kabul.
In a WhatsApp message to AFP, Taliban spokesman Zabihullah Mujahid said insurgents "blew up an American vehicle in Char Dara district of Kunduz" overnight Sunday-Monday. He said "several" other US and Afghan forces were also wounded.
US Forces-Afghanistan said one American service member was "killed in action" on Monday.
A US official told AFP that the service member had been inspecting a weapons cache when it exploded.
"This was not the result of an attack as the enemy claims," the official said, speaking on condition of anonymity.
Kunduz province is in northern Afghanistan and has been the site of repeated insurgent attacks and attempts to seize Kunduz city itself.
- Deadliest year -
Depending on how one qualifies a combat-related death, about 20 American troops have been killed in action in Afghanistan this year following Monday's announcement.
That makes 2019 the deadliest for US forces since combat operations officially finished at the end of 2014, and highlights the woeful security situation that persists across much of Afghanistan.
About 2,400 US troops have been killed in Afghanistan since the US-led invasion in October 2001.
Currently, the Pentagon has 12,000-13,000 troops in Afghanistan. Trump has said he wants to cut that number to about 8,600 or lower as he seeks to show voters he is making good on a campaign pledge to end America's longest war.
The deal between the US and the Taliban had been all but signed before Trump nixed it at the last moment, though a relative improvement in Kabul's security situation and the release of two Western hostages in a prisoner swap paved the way for a resumption of talks on December 7.
Those talks were paused for a few days following the Bagram attack, but have since started again.
The initial version of the deal would have seen the Pentagon pull thousands of troops out of Afghanistan in return for Taliban guarantees they would tackle Al-Qaeda and the Islamic State group.
But some members of Trump's own Republican party, including close confidant Senator Lindsey Graham, say the idea of the Taliban conducting counter-terrorism operations is risible.
Monday's attack comes one day after officials announced preliminary results in Afghanistan's presidential elections that put President Ashraf Ghani on track to secure a second term.
The Taliban have long viewed Ghani as an American stooge and have refused to negotiate with him.
Also Monday, a bomb explosion at a funeral ceremony in Laghman province east of Kabul killed three civilians and wounded nine others, interior ministry spokesman Nasrat Rahimi said.
He blamed the Taliban for the blast that hit the crowd of mourners at a local tribal leader's funeral.
The Taliban were not immediately available to comment.