A member of Nangarhar’s provincial council, Ajmal Omer, told The Associated Press that the gunman was killed. There have been numerous attacks by Afghan national army soldiers on their allied partners during 18 years of America’s protracted war in Afghanistan.

Six US service members have been killed in Afghanistan since the start of 2020, including Saturday’s casualties. Last year, 22 US service personnel died in combat there.

An Afghan Defense Ministry official, who was not identified because he was not authorized to speak to the media, said the shooter was an Afghan soldier who had argued with the US forces before opening fire. He was not a Taliban infiltrator, the official said.

In a statement, the US military said “an individual in an Afghan uniform opened fire on the combined US and Afghan force with a machine gun. We are still collecting information and the cause or motive behind the attack is unknown at this time.”

Omer, the provincial council member, is from Nangarhar Province’s Sherzad district, where he said the incident took place. An Afghan soldier was also wounded, Omer said.

The US military said American and Afghan military personnel were fired on while conducting an operation in Nangarhar Province.

Last July, two US service members were killed by an Afghan soldier in the southern Kandahar Province. The shooter was wounded and arrested. In September, three US military personnel were wounded when a member of the Afghan Civil Order Police fired on a military convoy, also in Kandahar.

Washington’s envoy Zalmay Khalilzad has been meeting with Taliban representatives in the Middle Eastern state of Qatar in recent weeks. He’s seeking an agreement to reduce hostilities to get a peace deal signed that would start negotiations among Afghans on both sides of the conflict.

There are roughly 12,000 American troops in Afghanistan, and the Pentagon is planning to reduce the number to 8,600 in the next few months, with or without a signed peace deal.

Twenty American troops died during combat operations in 2019, the most in any year since 2014.

In his State of the Union Address on Tuesday, President Donald Trump referenced the peace talks, saying U.S. soldiers were not meant to serve as “law enforcement agencies” for other nations.

“In Afghanistan, the determination and valor of our warfighters has allowed us to make tremendous progress, and peace talks are now underway,” he said.

The Taliban today hold sway over practically half of Afghanistan, staging near-daily attacks that target soldiers, security forces and government officials but also kill civilians.

The US first invaded Afghanistan in 2001 under the banner of fighting “terrorism.” The invasion toppled the Taliban, but the terror group has never stopped its attacks.

More than 32,000 civilians have been killed in the conflict, according to the United Nations.