Mr. Morales, Bolivia's first Indian head of state, is pressing Congress to convene a constituent assembly that would draft a new basic law for the Andean nation -- something that can only be done with approval from two-thirds of the bicameral Congress.

But with his Movement to Socialism (MAS) party controlling a little less than half the seats in each chamber after December elections, he faces tough opposition from conservative parties that fear he plans to enshrine left-wing policies, including state ownership of Bolivia's abundant oil and gas resources.

Mr. Morales has urged peasants and the army to rally to his support. Other MAS leaders have called for popular mobilizations against "conspiracies" led by multinational corporations, which, they say, are trying to destabilize the government.

Leaders of the right-wing Podemos party and regional authorities of the newly autonomous eastern departments fear the constituent assembly will be dominated by MAS.

Mr. Morales is proposing that each of the country's 70 voting districts elect a three-member delegation to participate in the assembly. Any party that wins a simple majority in a district would get to choose all three members.

MAS holds an overwhelming majority in the western part of Bolivia, and the opposition parties fear this would allow Mr. Morales to pack the assembly with his supporters from the high Andean plain.

Just what the constituent assembly will be asked to do is not clear. There have been vague proposals by Mr. Morales and other government ministers that a new constitution enshrine the nationalization of natural resources and guarantee majority Indian representation in Congress.

"We are going to assure that the original indigenous peoples participate directly in re-founding Bolivia, as they were not represented when the republic was first formed in 1825," Mr. Morales said recently.

But Senate leader Oscar Ortiz of Podemos complained in an interview that "despite repeated inquiries" by members of Congress, the government has not announced what proposals the constitutional assembly is being called to decide.

Opposition leaders also are concerned about other recent measures they see as an effort to extend MAS control.

The government recently ordered a 50 percent cut in the salaries of legislators and public servants, saying the money was needed to finance health and education.

But opposition leaders say the cuts will be felt most acutely by top-earning judges and government lawyers. "The effect it's going to have is that professionals will leave the government, creating .. the space for militants of MAS to be appointed to fill vacancies," Mr. Ortiz said.

The Morales government replaced 28 top-ranking generals in its first week in power and a high-level source within MAS said the administration soon expects to "clean out" the Supreme Court by investigating its members for corruption.

Chief Justice Eduardo Rodriguez, who served as interim president until Mr. Morales took office, resigned from the court Thursday without explanation.

MAS has combined democratic methods with street tactics during its rise to power. Mr. Morales won the presidency after his party orchestrated violent protests to topple the government of President Carlos Mesa last year. MAS similarly ousted President Gonzalo Sanchez de Lozada in 2003.

Mr. Morales said recently he was informed by his new military chiefs of a plot to destabilize his government. Speaking before the Tupac Katari peasant federation in La Paz last Monday, he accused "transnationals" of conspiring with the "oligarchy" against his plans to nationalize Bolivia's natural resources.

Mr. Morales was joined by his vice president, one-time Tupac Katari Guerrilla Army leader Alvaro Garcia Linera, who is considered a moderating voice in MAS.

Mr. Garcia said the MAS mobilizations are "to protect the president, to defend the nationalization, to defend ourselves from the gringos, to defend the constitutional assembly."