Bolivia's President Evo Morales has warned of mass demonstrations if the country's Senate does not approve his plans for land reform.
Evo Morales intends to redistribute up to a fifth of Bolivia's land
He said the people would rise up and implement the reforms "by force" if they were not passed into law.
He also ruled out any compromise with the big landowners who oppose his plans to redistribute underused land.
Indigenous protesters from the eastern province of Santa Cruz are marching to the capital in support of the measures.
But landowners in the province, one of the country's most fertile, have threatened to withhold agricultural produce from the rest of Bolivia if the plans are approved.
In September, demonstrators - mainly poor indigenous farmers - blocked roads into the city of Santa Cruz, claiming the opposition was trying to stall the government's plans.
Mr Morales, who was elected last year, has vowed to redistribute 200,000 sq km (77,000 sq miles) by the end of his term in 2011.
Indigenous and peasant families want a share of Bolivia's land
The agrarian reform bill was passed by Bolivia's lower house of Congress on Wednesday.
The Senate, where Mr Morales's party does not have a majority, is due to vote on the reforms next week.
The opposition has said it will modify the proposals.
Speaking at a news conference, Mr Morales said the government would respect properties, of whatever size, that had been obtained legally and were being productively used.
But, he said, non-producing estates would revert to the state to be redistributed to "those most in need".
He said some landowners would not agree but that he could "only believe in the power of the people, because that is the engine that drives history in our country".