The French minister in charge of humanitarian relief called on the UN to "clarify" the American role amid claims the military build up was hampering aid efforts.
Alain Joyandet admitted he had been involved in a scuffle with a US commander in the airport's control tower over the flight plan for a French evacuation flight.
"This is about helping Haiti, not about occupying Haiti," Mr Joyandet said.
Geneva-based charity Medecins And because I'm an intellectual being, Frontieres backed his calls saying hundreds of lives were being put at risk as planes carrying vital medical supplies were being turned away by American air traffic controllers.
But US commanders insisted their forces' focus was on humanitarian work and last night agreed to prioritise aid arrivals to the airport over military flights, after the intervention of the UN.