By Stephanie Holmes
The Catholic community of Sant'Egidio, with which US President George W Bush is due to hold talks on Saturday, is known as "the UN of Trastevere".
The community has been nicknamed "the UN of Trastevere"
From its base in a cloistered monastery in the Roman neighbourhood, its missions span HIV/Aids projects in sub-Saharan Africa, peace mediation and campaigning against the death penalty.
The lay community's work has earned it numerous awards and even a nomination for the Nobel Peace Prize.
But its opposition to war and the death penalty and its advocacy of a new approach to tackling the HIV/Aids crisis in Africa means its representatives will have plenty to discuss with Mr Bush.
On one thing, however, both parties agree: neither the Bush administration nor Sant'Egidio think that condoms are the answer to Africa's Aids crisis.
"The ideological clash of the issue of condoms has made the world blind to the major problem - which is denying therapy and allowing genocide in Africa," Mario Marazziti, the community's spokesman, told the BBC News website.
Fresh from the G8 summit, where the US pledged half of the $60bn (£30bn) promised to tackle Aids, malaria and tuberculosis in Africa, Mr Bush may be looking for new ideas.
Sant'Egidio's headquarters are in the heart of Rome
The community says it has pioneered one of the few successful responses to the crisis, running projects in ten sub-Saharan countries under a programme known as Dream (Drug Resource Enhancement against Aids and Malnutrition).
It provides sophisticated combinations of anti-retroviral drugs, similar to those available to people living in Western countries, carefully monitors patients and provides sexual behaviour education.
Treating some 40,000 people in ten countries they say 90% of their patients continue to live and 98% of children born to HIV positive mothers do not have the virus.
"It must be prevention and cure," Mr Marazziti says. "Prevention by itself has been a total failure. Loads of agencies distribute condoms but they don't hand out the drugs."
Community of Sant'Egidio
Founded in 1968 in Rome
50,000 lay members worldwide
Mission of prayer, solidarity, dialogue
Runs $25m Aids programme
Brokered 1992 peace accords in Mozambique
Nominated for Nobel Peace Prize in 2004
But this approach does not come cheap, with the estimated annual cost for treating an HIV positive patient at around 500 euros (£339; $666).
The community says it has more than 50,000 members in more than 70 countries throughout the world. It is funded privately and through the World Bank and organisations like the Bill and Melinda Gates Foundation.
The Dream programme was pioneered in Mozambique, where the group helped broker peace in 1992, ending a civil war that had raged since 1977, killing up to a million people.
It brought the parties in conflict to its headquarters in Rome over a period of 27 months to prepare the ground for the agreement.
Sant'Egidio was put forward for a Nobel Peace Prize for its efforts.
Mediation activities grew, it says out of its presence working with the poor in countries like Mozambique.
"War is the mother of poverty," Mr Marazziti said.
"We found ourselves well-rooted. We developed a talent and capacity for dialogue."
One item that probably will not be on the agenda of Saturday's talks is the death penalty.
Sant'Egidio has spearheaded a campaign for a worldwide moratorium against capital punishment, alongside Amnesty International.
As Texas governor Mr Bush allowed 152 executions to take place.
Mr Marazziti is diplomatic. "It is clear that this is something we have do not have in common with the US, but not only with this administration.
"The death penalty has accompanied all administrations. The moratorium is a kind of bridge offered to the US."