JOHANNESBURG -- Land activists and militants opposed to the Earth Summit said here they would join forces on Saturday to stage a mass protest march, promising to make 20,000 of the world's poorest descend on the UN gathering.

South Africa's Landless Peoples Movement (LPM) said it had decided to join a march organized by the Social Movement Indaba (SMI), a loose gathering of groups opposed to globalization and to the summit.

"We have decided to come together. We are fighting the same battle here," said Mangaliso Kubheka, the LPM's national organizer. The SMI's Trevor Ngwane added: "We are marching from the poor working class township of Alexandra to the rich area of Sandton, probably the richest suburb in Africa, with a message to the Fat Cats at the summit."

They were speaking at a joint press briefing outside Soweto, southwest of Johannesburg where thousands of LPM members are squatting in a dilapidated cinema complex and preparing for the march.

The five-kilometer (three-mile) route will take the protestors to the heart of Sandton, where the 10-day summit is taking place at a 6,000-seat Convention Center.

"This is going to be a militant march, but we will make sure that discipline will be maintained at all times," promised march organizer, Andile Mngxitama, who said if violence broke out, it would be coming from the police's side.

He said activists from La via Campesina, an international movement representing peasant workers and farmers, would also join the march.

"We are proud to join this demonstration with our comrades," said Gianni Fabbris, a Campesina spokesman.

Tension between the South African government and various non-governmental organizations reached boiling point over the past two weeks after police broke up protests by both the LPM and the SMI.

But the war of words eased on Wednesday, when local authorities granted activists permission to the stage the march from Alexandra.

It is one of three marches expected on Saturday, AFP reported.

Also protesting are international society for Krishna and the global people's forum, a coalition of South African trade unions, non-governmental groups and members of the ruling African National Congress (ANC).