Al-Jazeera television today broadcast a 25-second, silent videotape showing Briton Norman Kember and two other hostage Christian Peacemaker activists in Iraq.
Al-Jazeera said the men asked their governments and countries in the Persian Gulf to work for their release.
Maxine Nash, a member of the Christian Peacemaker Teams in Baghdad, said the missing man was American Tom Fox, 54, of Virginia. The hostages shown were Norman Kember, 74, of London; and Canadians James Loney, 41, and Harmeet Singh Sooden, 32.
The hostages disappeared on 26 November and the previously unknown Swords of Righteousness Brigades had claimed responsibility. The tape broadcast today carried a 28 February date.
The four were last seen together on a videotape, also broadcast by al-Jazeera, on January 28. It was dated seven days earlier.
Today's tape showed the three men sitting in chairs and speaking, although there was no sound. One of those on the tape had white hair and a slight beard, the two others had dark hair and full beards.
In the 28 January broadcast the al-Jazeera newsreader said the hostage-takers issued a statement saying it was the "last chance" for US and Iraqi authorities to "release all Iraqi prisoners in return of freeing the hostages otherwise their fate will be death". No deadline was set.
Christian Peacemaker Teams, a Chicago-based organisation, has been working in Iraq since October 2002, investigating allegations of abuse against Iraqi detainees by American and Iraqi forces.
Its teams host human rights conferences in conflict zones, promoting peaceful solutions.
Also still held hostage is American reporter Jill Carroll, who the Iraqi interior minister has said was being held by the Islamic Army in Iraq, the insurgent group that freed two French journalists in 2004 after four months in captivity.
Bayan Jabr, who is in charge of Iraq's police, also said he believed the 28-year-old freelance reporter for The Christian Science Monitor was still alive, although the deadline set by her captors for the US to meet their demands expired late last month.
Three videotapes provided by the kidnappers to Arab satellite television stations identified the group holding her as the previously unknown Revenge Brigades. She was seized on 7 January in Baghdad and her translator was killed.Reuse content