Some 1,600 workers resumed work Thursday after 150 indigenous people agreed to end their three-week occupation of a construction site for a huge hydro-electric dam in the Brazilian Amazon.

"The chiefs of several tribes have agreed and the others have followed," said Cleanton Ribeiro, a spokesman for the Indigenous Missionary Council in the nearby town of Altamira.

He said the natives have been waiting "for more than a year" for promises made by the public consortium Norte Energia, which is in charge of the Belo Monte project.

The activists, including members of the Xicrin, Juruna, Arara, Aweti, Assurini and Parakanawa tribes were demanding the presence of Norte Energia chief Carlos Nascimento.

After two days of hard-nosed negotiations, Nascimento pledged to "respect past commitments by respecting the culture of these peoples" affected by the construction of the dam across the Xingu River, a statement said.

Norte Energia notably agreed to build schools and health clinics for the indigenous people and to provide them with transport vehicles.

The consortium said it could not determine the financial loss caused by the work suspension, the longest since construction began a year ago.

Norte Energia says some 17 socio-economic and environmental projects worth $117 million have already been launched in the region.

The third largest dam in the world, the 11,200-megawatt Belo Monte is one of several hydro projects meant to provide Brazil with clean energy for its fast-growing economy.

Work began a year ago, despite fierce opposition from local people 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.

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, although some NGOs put the number at 40,000 displaced.

The federal government plans to invest a total of $1.2 billion to assist the displaced, by the time the dam is completed in 2019.