Thousands of anti-globalisation protesters have marched through the Venezuelan capital, Caracas, at the start of the World Social Forum.
More than 60,000 people have signed up to attend the forum
The protesters shouted anti-war slogans and many of them carried banners criticising US President George W Bush.
The annual meeting is seen as an ideological alternative to the World Economic Forum, attended by business leaders in the Swiss resort of Davos.
Delegates will discuss fair trade, debt forgiveness and indigenous rights.
The country's President, Hugo Chavez, is attending the six-day forum.
Some 10,000 people from 54 countries joined the anti-war march in Caracas.
Peace activist Cindy Sheehan, the mother of an American soldier killed in Iraq, addressed the crowds, saying the US needed to bring its troops home immediately.
Other speakers will include Argentine Nobel Peace Prize winner Adolfo Perez Esquivel, Uruguayan writer Eduardo Galeano and former French First Lady Danielle Mitterand.
Organisers say more than 60,000 people have registered to take part in seminars, workshops and panels to be held across the capital over the next six days.
US peace activist Cindy Sheehan led calls for an end to war in Iraq
The event is backed by funding from the Venezuelan government, which has reportedly subsidised the travel of some Latin American delegates.
Many of those marching shouted slogans praising Mr Chavez, who is also expected to address the conference.
The BBC's Greg Morsbach in Caracas says some delegates are concerned the forum may lose its global outlook and instead be dominated by debates surrounding big social changes in Venezuela.
However, others say they are happy to learn about the government-sponsored social projects designed to improve education and health care, our correspondent adds.
The World Social Forum was first held in the southern Brazilian resort of Porto Alegre in 2001, as an "antidote" to the big-business World Economic Forum.
It strongly opposes globalisation and wants both the corporations and the governments of the West to do more for the people and nations of the developing world.