A US doctor who survived after contracting Ebola while doing missionary work in Liberia has told how he feared he would die.

Dr Kent Brantly said he is "very close" to another doctor recently diagnosed with the disease and has spent time in "tearful prayer" for him.

Earlier, officials with the North Carolina-based missionary group Serving In Mission had announced the other doctor, a male obstetrician, had contracted the disease.

In the interview with US TV station NBC News, Dr Brantly said he feared his own death, telling a nurse at one point: "I'm sick. I have no reserve and I don't know how long I can keep this up."

At one point, Dr Brantly was asked whether he was told he might not survive.

"I don't think they ever said, 'Kent, I think you are about to die.' But I felt like I was about to die," he said.

NBC News said the interview was conducted in Asheville, North Carolina, where Dr Brantly and his family have been in seclusion since he was released last month from Emory University Hospital in Atlanta.

Dr Brantly and a female missionary from Serving in Mission were evacuated to the US for treatment after contracting Ebola in Liberia.

The two recovered after receiving an experimental drug known as ZMapp. The manufacturer says it has run out of supplies of the drug and it will take months to produce more.

Dr Brantly recalled waking up the morning of July 23 feeling "a little off" with a temperature of 100F (38C). After falling ill, he said he felt grateful his family had returned to the US days earlier.

"I was so thankful that Amber and the kids were not there. That would have been an overwhelming mental burden if I had woken up sick lying in bed next to my wife with one of my children snuggled up next to me," he said.