Sting told a news conference Sunday in Sao Paulo the decision to build the Belo Monte dam should be made by all Brazilians, especially the native communities that would be most affected.
The multi-billion dollar project would dam the Xingu River in Brazil's north.
Brazilian officials say the dam is needed to meet the energy demands of its growing economy, while environmentalists say it will swallow rain forest, kill off native fish and displace thousands.
Sting founded the Rainforest Foundation in 1989 after meeting a group of Amazon Indians.
