LA PAZ, Bolivia -- Bolivian President Evo Morales is insisting that a bid for broad autonomy by the country's largest and richest state is "illegal," "anti-constitutional" and "dictatorial."

But Morales warned Santa Cruz leaders not to use the referendum, which is expected to pass handily, to justify withholding federal taxes, calling it "the worst mistake they could make."

The president dismissed fears of violence over the separatist movement and showed little concern over the vote -- perhaps the biggest challenge to his two-year-old presidency -- during a half-hour interview with The Associated Press at the presidential palace late Friday.

"Seems to me like they've brainwashed you guys when you ask me, 'What's going to happen?' " Morales teased a reporter while leaning forward in one of the many gold-painted chairs crowding the palace's third-floor Golden Parlor.

"May 5," he said, referring to the day after the vote, "will be just another day."

Bolivia's president says he needs a strong central government to spread Santa Cruz's wealth to the rest of South America's poorest country. His proposed constitution includes a bill of rights and more autonomy for indigenous groups, which were shut out of the political system for centuries by a white and mestizo, or mixed-blood, elite.

If Santa Cruz leaders stop sending tax money, Morales said it will reveal their cause as "just a money grab."

"They're only in it for the money, not for the country. They're only in it to help out a few businessmen, and not the people," he said.

Asked if the government would use force to recover its money, Morales simply quoted advice he once received from Brazilian President Luiz Inacio Lula da Silva.

"He told me, 'Evo: patience, patience, patience,' " Morales said.

But the president's patience could be tried even further: Five more of Bolivia's nine states, most in Bolivia's relatively prosperous lowlands, may follow Santa Cruz's example with their own autonomy votes.

The vote is as much about race as it is about money: The referendum pits Morales's Indian backers in the western highlands against eastern Santa Cruz's largely mestizo population.

Each group claims to represent Bolivia -- but Morales points out that mestizos, by definition, prove his argument that the South American nation is an indigenous country at heart.

"Who among us doesn't have Quechua or Aymara blood?" he said, adding that Ruben Costas, the ruddy-cheeked, mustachioed Santa Cruz governor, "has Quechua blood."

On Friday, Morales suggested that the question of state autonomies might best be resolved by a nationwide referendum -- even though a national vote failed to resolve the issue two years ago.

Morales campaigned ferociously against a 2006 ballot measure on autonomy, helping to spur his conservative opposition's passion for the cause.

The movement gained momentum again last year, when Morales backers and Santa Cruz delegates locked horns over autonomy in an assembly convened to rewrite Bolivia's constitution.

The state delegates eventually walked out and drew up their own rules: an autonomy declaration so ambitious it would permit Santa Cruz to sign its own international treaties.

Morales said Friday he would be willing to work some of the Santa Cruz demands into his constitution, if voters nationwide approved.

"Maybe we're wrong to defend the new constitution exactly as it's been drafted," he said.

But he made it clear that the constitution takes precedent over any autonomy demands.

"First the mother," Morales said. "Then comes the son."