A terror suspect held in a UK jail has made a video appeal for the release of Briton Norman Kember, one of four Westerners being held hostage in Iraq.
Radical cleric Abu Qatada, detained since 2002, urged the kidnappers to free the men "in line with the principle of mercy of our religion".
Abu Qatada, who is being held at Full Sutton jail, near York, had volunteered to be filmed, the Foreign Office said.
Mr Kember, 74, of Pinner, London, was seized in Baghdad on 26 November.
The kidnappers claim to belong to a group called the Swords of Truth.
On Thursday, Arabic TV station al-Jazeera said the kidnappers had extended a deadline they set, under which the four men would be executed, by 48 hours until Saturday.
'Principle of mercy'
The kidnappers had originally said the men would be killed if Iraqi detainees in the country were not freed by Thursday.
New video footage has emerged of what appears to be two of the hostages in Guantanamo Bay-style orange jump suits.
Foreign Secretary Jack Straw repeated a request for the men's release.
He said: "The message of this latest statement is not clear. If the kidnappers want to get in touch we want to hear what they have to say."
BBC World Affairs Editor John Simpson said the reported two-day reprieve suggested negotiation efforts may be having some positive effect.
He also said it was unclear how much influence the Abu Qatada appeal would have on the actions of the kidnappers.
The terror suspect said on the video: "I am your brother Abu Qatada, Omar bin Mahmud Abu Omar, who is imprisoned in Full Sutton jail in Britain.
"I urge my brothers in the Brigades of Swords of Right in Iraq to release them in line with the principle of mercy of our religion, if there was no compelling religious duty against it."
The video, recorded on Tuesday, is being broadcast in the Middle East.
Qatada, described by a Spanish judge as al-Qaeda's ambassador in Europe, was briefly released under a control order earlier this year before being re-arrested pending deportation to Jordan.
He had originally been detained in October 2002. The authorities had been trying to track him down since December the previous year.
He has been found guilty of terrorism offences in a Jordanian court in his absence.
The Home Office said no leniency deal had been made with the terror suspect.
Mr Kember had travelled to Iraq with international peace group Christian Peacemaker Teams (CPT).
He was taken hostage with Canadians James Loney, 41, and Harmeet Singh Sooden, 32, and American Tom Fox, 54.
The kidnappers accused the men of spying for foreign forces in Iraq.
A new statement from Mr Kember's family said he was "a very kind and talented man and he has always tried to use his gifts to help others to make the world a better place".
The kidnappers want their demands to be met by Thursday
He was in Iraq "because he wanted the Iraqi people to know that there are many people who are sorry for all their suffering", it said.
It also thanked people for their messages and 25 Muslim groups which have called for the hostages to be released.
It concluded: "This is an extremely worrying, stressful time for all of Norman's family.
"We are praying with people from all faiths for the safe release of Norman and his friends."
On Tuesday new footage showing Mr Kember calling for UK troops to be pulled out of Iraq emerged.
Meanwhile anti-war envoy Anas Altikriti, an Iraqi, has travelled to Jordan to try to secure the release of the four hostages.
He was sent to Baghdad by UK peace and Muslim groups and has been meeting different Iraqi organisations and speaking to the local media.