By Daniel Schweimler BBC South America correspondent

When he took office six months ago, President Evo Morales of Bolivia promised radical change. And so far he has fulfilled that promise, with much more to come.

Mr Morales says Bolivia needs a new constitution

He has already nationalised the oil and gas industries, started the process of redistributing land, cut the wages of public workers, including his own, and inaugurated the building of a factory that will make legal products from the coca leaf, normally used to produce cocaine.

But the former llama herder and coca-leaf grower believes that is not enough and wants to go further in radically overhauling Bolivian society, giving a greater voice to the majority indigenous population.

They feel that for generations they have been at worst exploited, at best ignored.

On Sunday, Bolivians will vote for 255 members of a new assembly that will then have one year to produce a new constitution. It will then be voted on by the people in a referendum.

The ballot paper will also ask voters whether their nine states should have greater autonomy. The governors are presently appointed by the central government.

Washington worries

President Morales's party, MAS, has said it will win at least 70% of the vote, ensuring that its supporters are in place to implement the radical changes their leader is calling for.

The president is hoping to build on the convincing victory he won in December's election and the work he has done since he took office.

Despite this huge support, Mr Morales's first months in office have not been without problems.

He has formed a strong partnership with Venezuelan President Hugo Chavez and the Cuban leader Fidel Castro, which has worried many in Washington and some Bolivians.

A radio advert put out by the opposition Podemos party says: "Chavez is sending soldiers to Bolivia. Say no to Chavez."

A huge rally on Wednesday demanded autonomy for Santa Cruz

In recent weeks, the government has been trying to distance itself from its Socialist friends and emphasis its independence.

But not all Bolivians are behind Evo Morales and his radical plans for the future.

There are growing calls in the oil and gas rich eastern province of Santa Cruz for greater autonomy from La Paz and even full independence.

Bolivia's wealthy elite has been watching developments with growing trepidation. The majority of Bolivians believe that that elite has mismanaged and plundered the country for too long.

But if the rich start to feel threatened, they may be tempted to take their wealth and technical expertise elsewhere.

President Morales is performing a delicate balancing act. He has to satisfy the hopes and expectations of a population that feels its been ignored for too long.