The four - Canadians Harmeet Sooden and James Looney, American Tom Fox and British citizen Norman Kember - were accused by their captors of working as spies for US forces in Iraq.
But CPT disputes the accusation, saying it "embraces the vision of unarmed intervention waged by committed peacemakers ready to risk injury and death in bold attempts to transform lethal conflict through the non-violent power of God's truth and love".
Several prominent Muslim groups in their respective countries as well as Iraq have called for their immediate release.
The Washington-based Council on American-Islamic Relations said in early December:
"The hostages in Iraq are long-time friends of the Muslim community. On numerous occasions they stood shoulder-to-shoulder with Muslims advocating for their causes - from forming human-shields in Iraq before the US invasion, to protecting the honour and property of the Palestinian people."
The influential Iraqi Association of Muslim Scholars said CPT and its activists in Iraq had a record of helping the poor and disadvantaged.
A video of the four CPT members' detention was broadcast on Aljazeera on 29 November.
Their captors had threatened to kill them unless Iraqi detainees were freed. An initial deadline was extended by 48 hours and the four have not been heard from since.
Their captors have not issued any new demands.
Aljazeera spoke with Doug Smith, a friend and colleague of Tom Fox, in Langley, Virginia.
Aljazeera.net: What was Tom doing in Iraq and how long had he been there?
Doug Smith: Tom joined Christian Peacemaker Teams in 2003 to serve as a full-time volunteer. CPT asked Tom if he would be willing to join their team in Iraq, and he agreed to go.
When he was abducted, Tom was in his 3rd tour in Baghdad. His tours there were: September 2004-December 2004, April 2005-July 2005, and he started his third tour in September 2005.
Tom's work is described in his blog. During his first tour, he spent considerable time helping Iraqi families with family members in prison obtain information on the status of their loved ones.
During his second tour, he helped organise a Muslim Peacemaker Team (MPT) with both Shia and Sunni members. The CPT and MPT teams spent time in Falluja helping, in a small way, to repair the damage to the city by picking up trash.
Fox (2nd from left) was helping
Iraqi Palestinians get to Syria
During Tom's most recent visit to Iraq, the team had spent some time helping Iraqi Palestinians to seek passage into Syria so they could stay in a refugee camp.
CPT has had an ongoing presence in Hebron, Palestine, for quite a while, and Palestinians have been among the most vocal in calling for the release of the four CPT hostages.
Much of CPT's work was listening to the concerns of ordinary Iraqi citizens and working to give a public voice to those who have no voice. They made a conscious decision to live in an ordinary Baghdad neighbourhood, outside of the Green Zone.
This was an act of courage on their part. Tom once told us: "Too many people are willing to die to wage war, too few are willing to die for peace."
Who funded his trip and his work there?
Each CPT volunteer is asked to help raise funds to support CPT's work. Tom asked for and received financial support from a number of groups and individuals, including Langley Hill Friends (Quaker) Meeting, where Tom is a member of the congregation, and the Northern Virginia Mennonite church.
The Quakers and Mennonites, along with the Church of the Brethren, are the primary sponsoring organisations for CPT.
Had he felt threatened at all by any armed force during his stay there?
Tom did not express any concerns to us about feeling threatened by armed forces. He shared a story, in an amusing way, of someone from the US government who was supposed to be addressing the plight of Iraqi Palestinians.
She had asked to meet with the CPT team about their work helping the refugees cross the Syrian border. She had never actually met any of the Iraqi Palestinians since she was confined to the Green Zone.
She agreed to meet with the CPT at their Baghdad apartment. As part of this story, Tom told how the woman travelled from the Green Zone in a convoy of Humvees and armed escorts.
Has Tom's family or CPT been contacted by his captors?
Not to our knowledge.
How have his family and friends coped with his abduction?
Obviously, we have all been concerned with the safety of Tom and his fellow captives, and hope for their safe return. However, Tom went to Iraq with his eyes open, knowing of the danger, but deciding courageously that being able to make a difference for Iraqis outweighed the personal danger.
At Langley Hill Friends Meeting, we have held a number of vigils, both public and private, praying for not only Tom and his fellow captives, but also for those who are holding them hostage. Many of these vigils have been shared by members of other faiths, including Muslims and Sikhs.
"Too many people are willing to die to wage war, too few are willing to die for peace"
Doug Smith, quoting his friend and colleague Tom Fox
Tom's family has tried to maintain their privacy during their ordeal.
There have been reports that some Christian missionaries slipped into Iraq to proselytise. Was Tom involved in this?
No, not at all. CPT is not a missionary organisation, and Tom was not there to proselytise.
Has the US government helped in securing his release?
I believe that CPT has consulted with the [US] government, but to our knowledge the government has not been actively involved in efforts to seek Tom's release.
Based on media reports, the Canadian and British governments have been actively involved in efforts to release the four hostages.
Media articles mentioned strong Muslim support for Tom's release. What have they done?
Locally, in the Washington area, we have received support from both the Council on American-Islamic Relations (CAIR) and the All Dulles Area Muslim Society (ADAMS). CAIR organised a news conference within a week of the kidnapping condemning it and calling for the release of the hostages. I participated in that news conference. There was an Aljazeera video crew there.
ADAMS invited Langley Hill Friends Meeting to co-sponsor a prayer service and vigil that was held on 9 December.
ADAMS and Langley Hill have had a close relationship since the events of 11 September 2001 and are primary organisers of the Northern Virginia Interfaith Women's Fellowship.
Pictures courtesy of Christian Peacemaker Teams