About 150,000 people demanded autonomy for Bolivia's wealthiest state late Wednesday in one of the nation's largest demonstrations ever just four days before a national referendum on the issue.

Bolivians will vote Sunday on whether to give the country's nine states more executive and financial powers at the expense of the central government.

Santa Cruz leaders are spearheading the "yes" campaign — maintaining that too much of the state's wealth is sucked away by the central government to subsidize Bolivia's poorer and more Indian western highlands.

Santa Cruz, whose state capital of the same name is 356 miles southeast of La Paz, has only 1.2 million of Bolivia's 8.5 million inhabitants yet generates a third of its wealth. Its lighter-skinned elite present the strongest opposition to President Evo Morales and his leftist policies.

Morales, the country's first Indian president, took power in January and has since nationalized the natural gas industry and accelerated land handouts to the poor. This has angered some large landowners in Santa Cruz.

German Antelo, president of the powerful Pro-Santa Cruz Civic Committee, said autonomy would bring "justice and solidarity" in Bolivia.

He also used the event to attack Morales' close relationship with Venezuelan President Hugo Chavez and Cuba's Fidel Castro.

The opposition has objected to the presence of an undisclosed number of Venezuelan military in the country, including air force pilots who shuttle Morales around in two Venezuelan helicopters, and say Chavez is trying to influence the election here.

"Enough with this advance toward communism ... enough with the meddling," Antelo told the crowd filled with people waving the Santa Cruz state flag.

Morales has said he will vote "no" in the referendum, claiming autonomy will only benefit "oligarchs" and not the majority poor population.

Some Morales allies fear that the autonomy movement is the first step of a plan by Santa Cruz to separate from Bolivia, while Santa Cruz leaders insist they just want to more efficiently manage their own tax revenues.

The referendum is happening alongside an election for an assembly which will rewrite Bolivia's constitution starting Aug. 6.

The referendum results are required to be taken into account by the constituent assembly which will be made up of 255 delegates. The assembly has a minimum of six months and as much as a year to make constitutional reforms which it must pass with a two-thirds vote.

Afterward, the new constitution will be put up for a national vote.