The parents of an American hostage threatened with beheading by jihadists were sent an audio message two weeks ago in which he told them: "My time is running out."
Ed and Paula Kassig, whose son Peter, an aid worker, was kidnapped in Syria last year, spoke of the tape during American television interviews after deciding to break their silence about his plight.
Mr Kassig, 26, a former US Army Ranger who was delivering food aid when he was captured in October last year, has converted to Islam while in captivity and is now known as Abdul Rahman.
He appeared in the latest beheading video released by the Islamic State of Iraq and the Levant (Isil), in which the British taxi driver Alan Henning was murdered. A jihadist in the video - which was released on Oct 3 - threatened Mr Kassig's beheading in retaliation for American air strikes.
The Kassigs said they had also received a private audio message from their son when the video was released.
It was the first time that the couple, from Indiana, had heard their son's voice in more than a year. "It was just automatic, kind of toneless, as though he was a robot," Mrs Kassig told CBS.
"He described that his time was running out," she added on NBC. "His vitality, his spark was not in his voice."
The couple also disclosed an extract from a handwritten letter that Mr Kassig was able to send them from captivity.
It read: "Don't worry, Dad. If I go down, I won't go down thinking anything but what I know to be true, that you and Mom love me more than the moon."
For much of the time that Mr Kassig has been in captivity, the couple were too scared to tell even those close to him what had happened.
Mrs Kassig said: "We couldn't answer honestly when people would ask us [what happened]. So we had to lie to our friends again and again and again."
But the couple said the fact that hostages including their son's cellmate, the American Steven Sotloff, had been killed despite their families abiding by the captors' instructions to keep quiet, had prompted a change of heart.
"The dynamics have changed now. Steven's family kept to secrecy, and he was executed. Peter's name has been listed," Mr Kassig said. "I'd love to see him again. We're doing everything we can to secure his release.
"I am hoping that he will somehow hear of this and of other conversations we've had or other times we've spoken in public.
"That way he'll know that we haven't forgotten him, we haven't abandoned him and we certainly do love him.
"I have to try. Because I need to know that I've done everything I can do. We will love him until the end of time."
The couple also disclosed that they had received repeated demands from the hostage takers, but were unable to meet them. "There's no room for dialogue," Mr Kassig said. "They demand. They simply demand."
Mrs Kassig added: "Their demands have always been ones that we cannot accommodate. We have sent them back messages that we cannot do what you ask. We have tried. But we don't have the power to do it. He [Peter] knows that this is bigger than it just being about him. And we do too."
Mr Kassig said that his son's conversion to Islam was genuine, telling NBC: "He was as taken with the religion as he was with the people. It was a natural process for him."