U.S. military commanders in Afghanistan are now authorized to target Islamic State militants seeking a foothold in the country's volatile Nangarhar province.
A U.S. military official on Wednesday called the move a "significant step."
"It is certainly a recognition of a long term potential threat," the official said.
The expanded mission comes only days after the U.S. State Department declared the Islamic State's franchise in Afghanistan — known as ISIL-Khorasan, or ISIL-K — a foreign terrorist organization. In turn, lawyers with the White House and Defense Department translated that into an official "hostile-force" designation, which includes expanded authorities for the troops deployed there, a Defense Department official said.
Previously, any U.S. airstrikes reportedly targeting ISIS militants in Afghanistan were limited to situations involving evidence that those militants were threatening U.S. or Afghan forces, the military official said.
The ISIS faction announced its formation in January 2015. It is based on the "Afghanistan/Pakistan region and is composed primarily of former members of Tehrik-e Taliban Pakistan and the Afghan Taliban," according to the State Department.
It is unclear whether any substantial command-and-control relationship exists between Afghanistan's ISIS adherents and the leaders of the group's strongholds in Iraq and Syria.
"We currently characterize [ISIS] as operationally emergent," Brig. Gen. Wilson Shoffner, a top spokesman for the Resolute Support Mission in Afghanistan, told reporters Tuesday.
"I'll define that as not having the ability to orchestrate or control operations in more than one part of the country at a time. We're not seeing [ISIS] elements in Iraq or Syria orchestrating events here in Afghanistan," Shoffner said.
U.S. intelligence suggests that ISIS is trying to establish a base of operations in Nangarhar province.
"They've largely been pushed back to the southern parts of Nangarhar province. That area is very, very rugged, it's very mountainous. It's on the border with Pakistan," Shoffner said.
The U.S. now has more legal authority to target ISIL-K than the Taliban. That, in part, reflects how the Afghan government views the Taliban as a political problem and potential partner in future negotiations.
"The Afghan government has said, with the Taliban, they are looking for a long term peaceful solution. They don't seem to view ISIL-K the same way," the military official said.
Army Gen. John Campbell, the top U.S. commander in Afghanistan, estimates there are between 1,000 and 3,000 ISIS fighters across Afghanistan.
Al Qaida also remains a threat. In October, Afghan special forces troops raided a large al Qaida training camp in a remote region near Kandahar and killed 150 to 200 al Qaida fighters, Campbell said.
ISIS "doesn't have the capability, I believe, to go to Europe and attack or go to the homeland. Left unchecked, it will. They've said they want to do that," Campbell said in December.
Andrew Tilghman is the executive editor for Military Times. He is a former Military Times Pentagon reporter and served as a Middle East correspondent for the Stars and Stripes. Before covering the military, he worked as a reporter for the Houston Chronicle in Texas, the Albany Times Union in New York and The Associated Press in Milwaukee.