The Brazilian government's public snub to the Organization of American States, environmental groups and leaders of indigenous communities raised the stakes in the controversy over its plans for the world's third largest dam.

The Belo Monte hydroelectric dam on the Xingu River in the northern state of Para is opposed by environmentalists who argue it will harm the pristine ecology of an Amazonian region and displace thousands of indigenous Brazilians, destroying their villages and settlements.

The government rejects those objections, saying the dam is needed to meet projected shortfalls in Brazil's energy needs and is vital for Brazil's economic growth. The Belo Monte will be the second-largest hydroelectric dam complex in Brazil, after the Itaipu Dam on the Brazilian-Paraguayan border, and the world's third-largest in installed capacity after the Three Gorges Dam in China.

At the OAS-sponsored meeting Wednesday in Washington, a Brazilian government delegation was to have met with the campaigners. Instead the government opted out and explained its boycott simply as an expression of its right to build the dam, leaving the critics demanding a more reasoned defense.

Opponents say the dam isn't needed because Brazil's energy needs can be met with a more efficient use of the existing national grid capacity.

The Belo Monte Dam's planned installed capacity of 11,233 megawatts would meet government targets to modernize the northern region and promote more industry there. Once connected to the grid, the dam's power generation capacity will be a boon to southern areas, where rapid industrialization is making demands on available electricity supplies.

Opponents say some of the demand can be met by cutting waste in the supply network. The critics also say the construction of the giant dam will open the way for other dams to be built along the northern rivers, with devastating consequences for the ecology and traditional indigenous communities.

Plans for the dam began in 1975 but were met with controversy. The plans were revived in the 1990s and new designs were ordered before the government in August 2010 signed a contract with Norte Energia after securing approval from the Brazilian Institute of Environment and Renewable Natural Resources.

In January this year the government issued an installation license despite intense controversy but a federal judge on Feb. 25 ruled against the construction. The court's intervention didn't last long, however, and a higher court on March 3 overturned the federal judge's order.

The government issued the license to construct the dam on June 1 but a federal judge again blocked construction on Sept. 28.

The OAS got dragged into the controversy after the Inter-American Commission on Human Rights, one of its autonomous bodies, issued a public plea to the Brazilian government to halt work on the dam. The petition angered the Brazilian government, which rejected the commission's request. Part of the anger was caused over the commission's emphasis on the humanitarian impact of the dam and the threat to livelihood of thousands of indigenous people.

Before announcing the boycott, Brazilian Energy Minister Edison Lobao said it is the right of Brazil's government to decide if it wants the dam built. Campaigners have vowed to continue their protests.