Left-wing terrorist groups are to join with street demonstrators fresh from battle in Seattle, in a corporate-style convention to discuss the path to power.
More than 2,500 delegates, including the notorious Revolutionary Armed Forces of Colombia (Farc), are gathering in Brazil for a conference of American revolutionaries.
Representatives from the Mexican Zapatistas, the guerrilla group championing American Indian rights, and the Black Panthers will also take part in the five-day event.
Manoel Lima Amarel, event co-ordinator, said: "We believe it is important for all oppressed Americans to support each other and to work as one."
Conference organisers chose the city of Belem on the banks of the Amazon because of its historical significance. In 1835 it was the site of a failed uprising by native Indians who were protesting against the slave trade.
Despite the presence of known paramilitary groups, the Brazilian authorities have not objected to the Humanities Against Neo-Liberalism summit.
The civil police in Belem will be listening out "for any inflammatory talk".
"But as long as these people behave themselves there won't be any problems," said a spokesperson.
The authorities have even allowed some delegates to camp inside school halls and sports centres, while others are staying free of charge at family homes in the community.
Magno Carvalho, founder of the Brazilian Solidarity Committee for the Zapatistas, said: "Support from Brazil has always been regarded as crucial to our movement's success. We hope this conference will encourage more people to join our cause.
"It's an opportunity to trade experiences and also learn new methods of action. If all the groups work together then there is every chance of success in the future."
Conference organisers insist that the convention will be peaceful and have banned delegates from exchanging techniques on guerrilla warfare.
"This summit is not about violence," said Mr Amarel. "It's about ideology. There are other ways to destroy the chains of capitalism without resorting to aggression."