"We need to bring our troops home immediately," Sheehan told the thousands of protesters taking part in the march that kicked off the six-day Forum on Tuesday. "We need to hold someone responsible for all the death and destruction in the world. We need to see George Bush and the rest of them tried for crimes against humanity."

The overarching WSF theme "Another World Is Possible" and opposition to "imperialism" and war are the common denominators among the broad range of organisations and individuals gathered in Caracas this week, where one of this year's three Forums is taking place. The first phase was held Jan. 19-23 in Bamako, Mali, and the third is scheduled for late March in Karachi, Pakistan.

The wide variety of organisations and participants was expressed by the multicoloured march, in which some 15,000 activists representing dozens of local and visiting organisations took part starting on Tuesday evening and stretching into the wee hours of the morning along two avenues in the southern part of the capital.

Some 70,000 participants had registered for the WSF as of Wednesday, for around 1,800 activities organised by just over 2,000 different civil society groups.

The march gave an idea of the wide-ranging interests and causes coming together at the Forum, in which leftist political leanings are the norm, as well as sympathy and support for Venezuelan President Hugo Chávez.

Chants like "Stop Bush", "No to War", "Peace for Colombia" and "Another World, Another Americas, Are Possible", were heard alongside pro-Chávez slogans in the demonstration.

Members of Venezuelan groups mixed comfortably with organisations from foreign countries, the largest of which came from Brazil, Colombia and the United States. There were big delegations from Brazil's left-wing Workers' Party (PT), the Colombian group Christians for Peace and Justice, the former guerrilla Guatemalan National Revolutionary Unity (URNG), and Grassroots Global Justice, a network of U.S. grassroots organisations that represent working-class communities and communities of colour.

Marching with Christians for Peace and Justice was Adriano de Jesús, from the Colombian province of Antioquia. He was holding up a sign with photos of victims of a massacre committed 10 years ago by right-wing paramilitaries in Valle del Cauca.

"We came to demand peace in Colombia, and to struggle to bring it about," de Jesús told IPS. "But we also came to learn and to find out if what they say is true."

That goal - getting a firsthand view of what the Chávez administration and its "Bolivarian social revolution" have been doing for the past six years - is shared by almost all of the participants in this week's gathering.

The wide range of social programmes carried out by the Chávez administration, ranging from a campaign that basically eradicated adult illiteracy, a chain of government shops selling subsidised staple items to the poor, and a programme bringing health care to the slums, fit nicely with WSF aims like fighting for a world without poverty and marginalisation and combating neoliberal, free-market policies.

The left-leaning Chávez also frequently gives voice to other priorities shared with the WSF, like opposition to the U.S. war and occupation in Iraq and to the U.S.-promoted Free Trade Area of the Americas (FTAA).

In addition, the Venezuelan government has provided at least eight million dollars in - mainly logistical - support to the WSF.

Chávez's participation "does not form part of the regular Forum agenda, and will be limited to an appearance in an amphitheatre at the invitation of Brazil's Landless Workers' Movement (MST) and the international organisation Vía Campesino," Julio Fermín, a member of the Venezuelan WSF organising committee, told IPS.

And just before the WSF comes to an end next Sunday, Chávez will meet in private with representatives from the Global People's Assembly Network, which has been among the leading organisers of the WSF since the first edition was held in Porto Alegre, Brazil in 2001 as a counterpoint to the World Economic Forum held annually in Davos, Switzerland.

The first of the six thematic areas at this week's WSF is "Power, politics and struggles for social emancipation". Most of the conferences, seminars and workshops fall under this heading, "because this is a political forum; the participating organisations take a political approach to the world," Eduardo Liendo, another member of the organising committee, told IPS

The other thematic areas are "Imperial strategies and popular resistance", "Alternatives to the predatory model of civilisation", "Diversity, identities and worldviews in the international social movement", "Work, exploitation and reproduction of life", and "Communication, culture and democratising alternatives".