The protesters are calling on the country's parliament to immediately pass an agrarian reform bill that has been stalled for more than two months.

The demonstrators have blocked at least three main roads into Santa Cruz, the country's most populous city as it prepares to host Expocruz, Bolivia's annual trade fair.

A spokesman for Evo Morales, Bolivia's leftist president, said that government officials would travel to the region, the country's economic hub, to negotiate with the protesters.

"This protest is damaging to the trade fair, the region of Santa Cruz, and the country as a whole," the spokesman, Alex Contreras, said.

"We'll do everything possible to lift the road blockades through dialogue."

Land reform

The proposed land reform law would let the government expropriate idle or illegally owned private land in Santa Cruz, an opposition stronghold and a leading voice in a movement for greater regional autonomy from central government.

Studies have shown a small group of landowners own 90 per cent of the country's farmland, while the rest is shared among three million indigenous peasant farmers.

Although protesters said that their intention was not to sabotage the trade show, the blockades might persuade many Bolivians not to attend the event, which begins on Friday.

While the government said it would try to lift the blockades, it has an ambivalent relationship with the Expocruz organizers, who did not invite Morales, Bolivia's first indigenous president, to inaugurate the fair as is customary.

Morales's drive to redistribute idle land to poor peasants has previously angered large landowners in the farming heartland surrounding Santa Cruz.