One U.S. service member was killed in Helmand province, Afghanistan, on Tuesday after stepping on an improvised explosive device, according to NATO.

The service member was conducting a train, advise and assist mission with Afghan forces as part of Operation Resolute Support, the NATO mission in Afghanistan that began in 2015 when major operations in the country began to wind down.

"On behalf of all U.S. Forces – Afghanistan, as well as Resolute Support, our deepest sympathies go out to the families and friends of those involved," said Gen. John Nicholson, commander of U.S. Forces Afghanistan and Resolute Support. "We are deeply saddened by this loss, but remain committed to helping our Afghan partners provide a brighter future for themselves and their children."

Another U.S. service member and six Afghan soldiers were also wounded.

The Pentagon has not yet released the name of the service member pending notification of next of kin.

Defense Secretary Ash Carter said his "thoughts and prayers are with the loved ones of the service member killed and all those injured.

"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," Carter said. "We will continue to work closely with the government of Afghanistan and our NATO partners to bolster the capabilities of the [Afghan security forces] so they can provide the people of Afghanistan the peace they deserve."