Officials have identified the victims as Staff Sgt. Bryan C. Black, 35, of Puyallup, Washington, Staff Sgt. Jeremiah W. Johnson, 39, of Springboro, Ohio, and Staff Sgt. Dustin M. Wright, 29, of Lyons, Georgia.
The two injured United States soldiers had been evacuated to the Landstuhul Regional Medical Centre in Germany and were in a stable condition, it added. Boko Haram, based south in Nigeria, has also staged several attacks in Niger.
Eight Niger soldiers and two USA troops were wounded.
The soldiers were killed Wednesday in southwest Niger while on reconnaissance patrol. The suspected militants who launched the raids belong to the al-Qaeda in Islamic Maghreb - a group affiliated to the al-Qaeda that is active in the North Africa region.
The Department of Defense released the names of three soliders killed in Niger on October 4th.
The officials weren't authorised to discuss the matter publicly so spoke on condition of anonymity. In a statement, U.S. Africa Command said the forces were with a joint U.S. and Nigerien patrol north of Niamey, near the Mali border, when they came under hostile fire.
The US and Niger forces were leaving a meeting with tribal leaders when they were ambushed. His awards and decorations includes the Army Good Conduct Medal, National Defense Service Medal, Global War on Terrorism Service Medal, Army Service Ribbon, Special Forces Tab, Ranger Tab, Parachutist Badge, Air Assault Badge, and Marksmanship Qualification Badge - Sharpshooter with Rifle. Mali, Mauritania, Niger, Burkina Faso and Chad are putting together a 5,000-strong G5 Sahel force to fight the growing threat from extremists in the vast Sahel region. "This is about black market resources which terrorists use to gain revenue that helps them recruit, expand and export attacks", the official said. The first units are expected to deploy in October and all battalions should be on the ground by March 2018.
That force will operate in the region along with a 12,000-strong United Nations peacekeeping mission in Mali, which has become the deadliest in the world for United Nations peacekeepers, and France's 5,000-strong Barkhane military operation, its largest overseas mission.