A British former prisoner of the US at Guantanamo Bay has called for the release of Briton Norman Kember and three other hostages held in Iraq.
Moazzam Begg told BBC Newsnight that seeing Mr Kember in an orange jumpsuit reminded him and his fellow ex-inmates of their ordeal at the US base in Cuba.
UK Foreign Secretary Jack Straw has urged the captors to make contact.
Meanwhile, former Beirut hostage Terry Waite has applauded Mr Kember's courage and backed calls for his release.
The Swords of Truth group had said it would kill its Western hostages if all prisoners in Iraq were not released by Thursday.
But a report on Arab TV network Al-Jazeera said that deadline had been extended to Saturday.
It also showed footage featuring Mr Kember and American Tom Fox dressed in Guantanamo Bay-style orange jumpsuits, blindfolded and bound by shackles.
Mr Begg said seeing these orange jumpsuits had prompted him to make the appeal.
He said: "When we were first granted release by Allah's mercy we came home to find that there were people who opposed the government in their brutal war waged against Afghanistan and Iraq and stood on the side of justice, and they were not Muslims.
"It is our sincerest belief that Norman Kember, the 74-year-old Briton and those with him are amongst those people, the many people who opposed this war from the beginning and were only in Iraq to promote human rights for the oppressed."
He added that he hoped these words would encourage the hostage-takers to show mercy to the men and set them free.
Mr Begg was held for almost three years by the US at its naval base in Cuba.
He was eventually released without charge and sent back to the UK with his fellow inmates in January.
Mr Straw reiterated on Thursday morning that Mr Kember and his colleagues were peace campaigners, "dedicated to helping others".
"As I've said before, if the kidnappers want to get in touch with us, we want to hear what they have to say," he said.
On the BBC's Today programme Terry Waite, who was taken hostage in 1987 while working as a church envoy, and held for five years, made "a plea for the release of this man".
"I applaud his bravery, I applaud his desire for peace," he said.
But he criticised Mr Kember for going into a "highly polarised" situation in Iraq: "I dispute, myself, the tactic he has used, to go out there and make that demonstration at this time."
Mr Kember, along with Mr Fox, 54, and Canadians James Loney, 41, and Harmeet Singh Sooden, 32, had travelled to Iraq as a "gesture of solidarity" with Canada-based international peace group Christian Peacemaker Teams (CPT).
Their captors have accused the men of being spies, a charge their employers deny.
In the video shown on al-Jazeera, Mr Kember is shown telling the camera he is "a friend of Iraq".
"I have been opposed to this war, Mr Blair's war, since the very beginning but I ask him now, and the British government, to do all that they can to work for my release and the release of the Iraqi people from oppression," Mr Kember says.
Mr Kember's supporters held a one-hour silent vigil outside Peterborough Cathedral on Thursday night to show solidarity with Mr Kember and his fellow hostages.