The three pipelines in the Los Monos gorge area were ruptured on April 2 by a landslide caused by heavy rains.
However, technicians have been unable to get to the site of the incident to repair the pipelines due to protests in the Chaco region, local press reported.
As a result, the flow of Bolivian natural gas to Brazil was cut almost 20% on Thursday, local press reported.
Gas exports to Brazil have fallen to about 21 million cubic meters (Mm3/d) in the last week from 26Mm3/d, local press quoted Gustavo Mas, the financial chief of the Bolivian unit of Brazil's federal energy company Petrobras (NYSE: PBR), as saying.
The supply of gas to Argentina could also be affected, said Hugo de la Fuente, head of Bolivia's hydrocarbons regulator.
Protesters in a land dispute in the Chaco region, 700km south of La Paz, have been blocking roads - including main routes connecting Bolivia to Argentina and Paraguay - in the area for six days.
The protests are also threatening water and electricity operations and diesel fuel supplies in Bolivia, officials said.
Technicians from Petrobras and Bolivian gas transport company Transredes, which own the pipelines, have reached the landslide area and will repair the pipelines in the next 10-15 days, Bolivia's VP Alvaro García said in a statement.
President Evo Morales is "very worried" about what is happening in the south of the country, especially because preventative measures were not taken despite similar accidents in the past, the statement said.
There is damage along 16km of the duct, which transports gas extracted by Petrobras from the San Antonio and Margarita gas fields.
Protesters in the towns of Villamontes and Yacuiba are claiming the vast Margarita gas field is on their land rather than in neighboring Tarija.
A government delegation led by defense minister Walker San Miguel traveled to the region on Thursday to negotiate an end to the protests, Bolivia's deputy minister of decentralization Fabian Yaksic was quoted as saying.
The situation is "critical and desperate" as electricity and water supplies in the region operate on gas, Tarija mayor Oscar Montes said in a radio interview.
Some 65-70% of the population in Tarija is affected by power rationing every six hours to avoid the collapse of the system, papers reported.
More than 400 vehicles have been stopped at roadblocks including trucks from Argentina carrying supplies of diesel fuel for the Bolivian market, which has begun rationing the fuel.
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