Brazil's Supreme Court has approved the resumption of work on the huge Belo Monte dam in the Amazon, which was halted earlier this month after protests from indigenous groups.
The preliminary ruling on Monday overturns an earlier ruling that ordered construction of the dam across the Xingu River, a tributary of the Amazon, to be stopped until indigenous peoples can testify before Congress.
However, the decision by Supreme Court President Carlos Ayres Britto could be revised when the court examines the case further, its website said.
The dam, expected to produce 11,000 megawatts of electricity, would be the third-biggest in the world, after China's Three Gorges facility and Brazil's Itaipu dam in the south.
A regional federal court, in the earlier ruling, had noted that when Congress approved the project in 2005, it called for an environmental impact study after the start of the work.
By law, the native communities had the right to air their views in Congress on the basis of the study, but this was not done, the court said.
Work on the dam began a year ago, despite fierce opposition from local residents and green activists.
Indigenous groups fear the dam will harm their way of life while environmentalists have warned of deforestation, greenhouse gas emissions and irreparable damage to the ecosystem.
"Avatar" director James Cameron and actress Sigourney Weaver have given their backing to dam opponents, drawing parallels with the natives-versus-exploiters storyline of their blockbuster Hollywood movie.
Belo Monte is expected to flood an area of 500 square kilometers (200 square miles) along the Xingu, and displace 16,000 people, according to the government. Some NGOs estimate that 40,000 people would be displaced.
Explore further: Pipeline that leaked wasn't equipped with auto shut-off