By Damian Kahya
BBC News, La Paz
Opposition senators in Bolivia have threatened to boycott the senate in protest against plans to redistribute land and rewrite the constitution.
Evo Morales intends to redistribute up to a fifth of Bolivia's land
The threat came as thousands marched through the streets of the second city of Santa Cruz to demonstrate against the controversial land reforms.
President Evo Morales hopes to redistribute up to 20 million hectares.
His supporters are heading to the capital, La Paz, to demand that the senate pass the land reform law.
The march was organised by regional businesses and autonomy groups in protest at proposed land reform laws.
Landowners in Santa Cruz province, one of the country's most fertile, recently threatened to withhold agricultural produce from the rest of Bolivia if the plans were approved.
But this is not the opposition's only grievance.
Mr Morales proposes to rewrite the country's constitution, but has only a slight majority in the assembly to do so.
His party recently passed a motion allowing them to rewrite the document alone, with a two thirds vote only required at the final stage, followed by a referendum.
Demonstrations for and against land laws have divided Bolivians
This will sideline the opposition.
One party has declared a hunger strike - the owner of Bolivia's Burger King franchise leading the action.
Another, the largest, has announced that it is to boycott the senate.
Opposition regional governors are also incensed. The president has proposed a new law limiting their power.
Six of the country's nine governors have now united against the central government.
But the president's own supporters are also marching to La Paz to demand the senate pass the land reform law.
Most of this is still posturing. But if a compromise is not reached soon, larger and more serious protests are likely.