The original deadline set by the Swords of Righteousness was Friday but has been reset to Saturday, the station said.
The station included video showing two hostages wearing robes and shackled with chains.
Norman Kember, 74, of London, Tom Fox, 54, of Clear Brook, Virginia, and the Canadians James Loney, 41, and Harmeet Singh Sooden, 32, were taken hostage in Baghdad two weeks ago.
They were working for the Christian Peacemaker Teams, an anti-war group.
The deadline was changed just hours after Abu Qatada, dubbed Al-Qaeda’s spiritual head in Europe, called from his prison cell for the release of the four foreign peace campaigners.
“I am your brother Abu Qatada, Omar bin Mahmud Abu Omar, who is imprisoned in Britain,” said Abu Qatada in a short video message on the Dubai-based Al-Arabiya television station and its rival Doha-based Al-Jazeera.
“I urge my brothers … the Brigades of the 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,” he said.
Britain’s Foreign Office said it had allowed the message to be recorded following a request from Qatada’s lawyers, but had no part in determining its content.
The four members of the Christian Peacemakers Teams non-governmental organisation were abducted in Baghdad on November 26.
Abu Qatada, a Palestinian-born cleric with Jordanian nationality, was arrested on August 11 among 10 foreigners on suspicion of causing a threat to national security in Britain.
Abu Qatada had been granted bail in March after having been detained in Britain since October 2002 under anti-terrorism laws.
Until his arrest in August, Abu Qatada was forced to live under a 12-hour evening curfew, with restrictions on who he can meet and on his access to mobile telephones and the Internet.
He was also prevented from preaching at mosques or leading prayers as part of the conditions for his release. Jordan has requested his extradition.
A Jordanian state security court has issued two 15-year jail sentences against Abu Qatada in absentia in 1998 and 2000 on charges of financing a banned Islamist extremist group, links with Al-Qaeda and plotting to attack Christian visitors to the holy lands.
Separately, veteran US civil rights leader Jesse Jackson said he was prepared to go to Iraq if he knew who to negotiate with and if it would help the plight of the hostages.
“If we knew who to meet with then we are ready,” he said, speaking on Al-Jazeera television.
Reverend Jackson, a staunch opponent of the US-led war in Iraq, pleaded with the captors not to kill the hostages because they are “neither soldiers nor spies.”
He called the war in Iraq “immoral” and repeated his call for a timetable for the withdrawal of US troops.
Reverend Jackson travelled to Iraq in 1991 to help secure the release of 500 westerners held at the time by the former regime of Saddam Hussein.