Defense Secretary Ash Carter on Tuesday said he was "deeply saddened" by the death of a U.S. service member while on an advisory mission in southern Afghanistan.
"I was deeply saddened to learn one of our service members was killed today and another wounded while engaged in our mission to train, advise and assist Afghan forces," Carter said in a statement.
"Six Afghan soldiers were also wounded in the [improvised explosive device] blast. My thoughts and prayers are with the loved ones of the service member killed and all those injured," he said.
The U.S. troops were on patrol when they encountered the roadside bomb, or improvised explosive device. They were part of NATO's Resolute Support mission to train, advise and assist Afghan forces. Six Afghan forces were also injured.
President Obama announced the end of the U.S.'s combat mission in Afghanistan in 2014 but has continued its training mission there, as well as a counterterrorism mission.
Obama has also twice revised his original troop drawdown schedule. He originally planned only an embassy presence of about 1,000 U.S. forces by the end of 2016, and now plans 8,400 forces there by the time he leaves office in January.
The U.S. has also beefed up "expeditionary" training missions to areas where the Taliban has posed a renewed challenge to Afghan forces, recently sending 100 U.S. troops to Helmand province to help secure the area.
Press secretary Peter Cook said the forces were sent to provide "training, advise and assist" work to Lashkar Gah, and to provide protection for those advisers. The advisers will assist the police zone headquarters and their leadership team, he said.
Carter said the event shows that Afghanistan remains a "dangerous place."
"This tragic event in Helmand province reminds us that Afghanistan remains a dangerous place, and there is difficult work ahead even as Afghan forces continue to make progress in securing their own country," he said.
"We will continue to work closely with the government of Afghanistan and our NATO partners to bolster the capabilities of the [Afghan National Defense and Security Forces] so they can provide the people of Afghanistan the peace they deserve."
There have been 11 combat-related deaths of U.S. service members in Afghanistan since the end of 2014.