U.S. forces from 506th Infantry Regiment, attached to 4th Brigade Combat Team, 101st Airborne Division (Air Assault) are currently stationed in Paktia, as well as Paktika and Khost provinces in the east.
The American casualties are the first U.S. combat deaths for the month of August.
The Pentagon identified the slain solider as Staff Sgt. Sonny Zimmerman, 25, of Waynesfield, Ohio, according to reports. Zimmerman was assigned to Alpha Co., 1st Battalion-506th stationed at COP Chamkani.
American forces in the 506th have suffered four casualties since arriving in the country in May, underscoring the fierce fighting between U.S. and Afghan forces against Taliban and Pakistani-based insurgent groups in eastern Afghanistan.
Foreign fighters are pouring into the eastern part of the country to take on U.S. and allied forces in what will likely be the final fighting season for American troops.
Pakistani-based terror groups like the Haqqani Network and others are calling upon “every house, every family” to send fighters into Afghanistan, Afghan army commanders stationed at the American base in Paktia province told The Hill in July.
The contentious provinces in eastern Afghanistan along the country's border with Pakistan were the last areas to be handed over from U.S. forces to Afghan National Security Forces in June.
The handover was part of the overall U.S. strategy to have all American combat troops out of Afghanistan by April 2014.
Shortly before the attack in Paktia, Gen. Joseph Dunford, the top U.S. commander in Afghanistan, ramped up pressure on Kabul to sign a postwar deal with Washington.
"There is no doubt that the bilateral security agreement is going to send a clear message first and foremost to the Afghan people and Afghan security forces and enhance their confidence to deal with the challenges that we will have to deal with collectively in the coming months," Dunford told The Associated Press in an interview.
American and Afghan negotiators are reportedly close to finalizing a postwar deal that would keep a U.S. force in Afghanistan to conduct counterterrorism missions and continue training local forces after 2014.
But Afghan President Hamid Karzai has yet to agree to the terms of the postwar pact.