President Evo Morales also distanced himself from the decision to break up a protest march Sunday. His announcement came hours after police released hundreds of activists when mobs of local people blocked roads and an airport to prevent the detainees from being taken out of the area.

"We repudiate the excesses yesterday at the march," Morales said, adding that a high-level commission including international representatives should be formed to investigate the crackdown.

Hours earlier, Defense Minister Cecilia Chacon resigned in protest over the police action against opponents of the highway, who include not just local indigenous peoples but also Bolivia's main highlands Indian federation.

In a brief televised address Monday night, Morales announced that he was suspending the highway project and would let the two affected regions decide whether to proceed with the Brazil-financed road. He offered no specifics, but on Sunday he said that a referendum on the road could be held in the two affected regions, Cochabamba and Beni.

The proposed 190-mile (300-kilometer) highway would connect Brazil with Pacific ports in Chile and Peru. Plans called for it to cross Bolivia's 600-square-mile (12,000-square-kilometer) Isiboro-Secure Indigenous Territory National Park, which is home to 15,000 indigenous people who live off hunting, fishing, gathering native fruits and subsistence farming.

The residents fear an influx of settlers would destroy their habitat, felling trees and polluting rivers. Environmentalists say the road would mostly benefit Brazilian commercial interests such as timber exporters while endangering a pristine nature preserve.

Police used tear gas and truncheons to break up a march Sunday by some 1,000 protesters who were marching to La Paz, the national capital Bolivia's highlands.

Officers detained the protesters and loaded them onto buses planning to drive them back to the eastern lowlands provincial capital of Trinidad, where the march began in mid-August.

But hundreds of people lit bonfires on the roadway, forcing authorities to detour to the airport in the Amazon town of Rurrenabaque. Residents of the town, however, had blocked the runway with barricades.

Authorities then backed down and let the detainees go.

"Given the attack by hundreds of people, the police pulled back to avoid confrontations," Interior Minister Sacha Llorenti said at a news conference in La Paz before the president made his comments.

Bolivia's national ombudsman, Rolando Villena, told Erbol radio "there was excessive use of force" by police. Protest leaders claimed a child was killed and other protesters, including children, were missing. Bolivia's Roman Catholic Church issued a communique saying a child had died but offered no details.

Llorenti denied that police used excessive force, saying officers acted Sunday only to "evacuate the marchers to guarantee their safety and protect them from physical harm" because pro-government groups were approaching to stop the march.

Vehement opposition to the road has been a dilemma for Morales, an Aymara Indian whose support for the highway has alienated many of the indigenous Bolivians whose support was crucial to his landslide re-election in 2009.

Morales, a coca growers union leader who is the first indigenous president of a country where more than two in three people are Indians, has been a passionate leader of the campaign to curb global warming.

But he has been less of an environmentalist at home, and insists the highway is essential to strengthening Bolivia's economy.

Analysts have noted that Cochabamba, one of the regions that would be affected by the proposed highway, is home to the coca growers who still work with Morales and are in favor of the highway.

The crisis has hurt the president, whose popularity fell to 37 percent this month, its second-lowest level since he was first elected in 2006.