Aid groups working in Afghanistan have accused the US of trying to "militarise" their work by attaching conditions to aid and grants.
A number of aid organisations have told Al Jazeera they have turned down funding from the US government as the money has strings attached to military operations.
One such stipulation is "battlefield clean-up", which tasks aid groups with working directly under military reconstruction teams.
Anne Richard, of the International Rescue Committee, told Al Jazeera: "Sometimes, military leaders assume that because we are in the same place, we share the same over-arching goals.
"Our goal is to help the Afghan people - ideally, they help themselves. The military's goal is to fight in a war and to provide security.
"They are motivated by US national interest, we are motivated by humanitarian causes, humanitarian principals."
Humanitarian groups said that in 2009 their fundraising fell $200 million short of what they needed to help the Afghan people.
But William Frej, the mission director for USAID, told the humanitarian news service, IRIN: "Militarisation of aid is a gross mischaracterisation of what actually happens on the ground.
"Without [counterinsurgency] and without the military's support, many of the humanitarian agencies - such as Oxfam - that raise such complaints would not be able to enter the areas once controlled by insurgents."
Beyond risks of being closely associated with the military, aid organisations also argue that they are simply better at delivering aid.
"I just don't think the military should be telling Americans if they want to work in humanitarian fields, they should go into the military," Richard said.
"I think that if Americans want to do this good work, perhaps even veterans, they should join our organisation."