US forces in Liberia declare that Ebola patients or their blood samples will not be transported by helicopter as it will pose potential health danger to that of troops.
The policy has raised concerns among American doctors involved in the international effort to counter the Ebola outbreak but the US military has no plans to alter its approach, a spokesman said.
"The mission inside Liberia of our troops does not include direct contact with patients, handling of patients, or of the blood samples," Rear Admiral John Kirby told reporters.
"I don't foresee any change from a Defense Department perspective. I don't see any change to the way in which our air crews and our aircraft are being used down there," he said.
But it was possible private contractors might be hired to fly patients or samples across Liberia, Kirby added.
The roughly 2,350 US troops in Liberia and 240 in Senegal are focused solely on constructing health clinics, providing logistical help and training health workers, with a small team of specialists handling blood samples at several mobile test labs, he said.
The New York Times reported that a senior official in the US Centers of Disease Control and Prevention, Dr Kevin De Cock, was dismayed when learning about the rules for American helicopters at a meeting this week in Monrovia.
De Cock called the policy "unacceptable," according to the Times, which obtained a record of meetings of the international task force overseeing the fight to contain the often deadly Ebola virus in West Africa.
In one case, the lack of air transport meant blood samples from a village had to be delivered by walking for four hours, the Times wrote.
"This has to change this week," De Cock was quoted as saying in the minutes of a Monday meeting.
But the Pentagon said it was a question of safety and resources, as the crew and helicopters did not have the training or equipment to handle patients or blood samples.
"Safety is obviously a number one concern, and those pilots and those crews ... they're not trained and they're not equipped to conduct those kinds of flights," Kirby said.
The Pentagon had initially planned to deploy nearly 4,000 troops to Liberia and Senegal but said last week it would only send about 3,000 forces after finding that some construction needs could be handled by local firms.
The Ebola outbreak, almost entirely confined to West Africa, has left 5,420 people dead out of a total of 15,145 cases since the virus emerged in Guinea in December, according to the World Health Organization.