One US soldier was killed and two others were injured in the southern Afghan province of Helmand where fighting continues between Taliban militants and Afghan Army forces, Brig. Gen. Wilson A. Shoffner - spokesman for US forces in Afghanistan - said in a statement on Tuesday.
"We can confirm a US helicopter has landed in Marjah, Helmand Province, and is experiencing mechanical problems. It was not shot down," said US Army Colonel Michael Lawhorn, spokesman for the Resolute Support mission in Afghanistan.
A medical helicopter was hit by mortar fire when US special forces were attacked during a joint American-Afghan counter-terrorism operation.
Pentagon spokesman Peter Cook also confirmed the killing of a US soldier in Afghanistan.
"My understanding is that there may still be Americans on the ground in this immediate situation engaging with the enemy in support of Afghan forces," Cook said. "This is a fluid situation."
US special operation forces alongside their Afghan partners have been trying to push back Taliban attacks in Helmand, which has been the focus of the Taliban in recent weeks.
The Taliban has a significant influence in Afghanistan where it controls various regions and claimed responsibility for killing six American troops on the US air base at Bagram in December.
The editor of The Long War Journal Bill Roggio, who follows Taliban moves in the region, says one-fifth of the country is controlled or contested by the Taliban.
The Taliban lost its control after the US invasion in 2001 but regained some districts between 2005 and 2009.
US President Barack Obama announced that he will withdraw US soldiers from Afghanistan in 2015, but Taliban attacks led to him postponing the decision to 2017.
Obama announced in October that an American force of 9,800 troops would remain in Afghanistan through most of 2016, before dropping to 5,500 in 2017.