Venezuela will hold a referendum on December 2 to decide on 69 proposed constitutional amendments.
On Friday Venezuela's National Assembly approved the constitutional changes that will expand Chavez's powers and allow him to run for re-election indefinitely.
"We're not going to allow them to fill Venezuela's streets with blood"
Hugo Chavez, Venezuelan president, on opposition rallies
The changes, which would implement "economic socialism", will also widen the president's decision-making powers regarding military affairs, the national reserves and monetary policy.
Chavez, first elected in 1999, will have to leave office in 2013 unless the rules are changed.
On Sunday he warned those opposed to the proposed constitutional reforms that they may not get rally permits.
Chavez told officials to come down hard on his opponents and not allow "these little rich kids born with a silver spoon in their mouth to destroy the streets of Caracas".
"The next time they announce one of these marches, we'll have to evaluate whether to grant permission," he said.
|Chavez supporters saying yes to his |
proposed charter changes [AFP]
"We're not going to allow them to fill Venezuela's streets with blood."
Chavez's warnings were in response to violence that erupted last week during street demonstrations led by university students.
Two students were killed and four others injured by gunfire during protests outside a university in western Zulia state.
Human rights groups, the Roman Catholic Church and other critics have accused Chavez of trying to consolidate power, pointing to the proposed elimination of presidential term limits under the reforms.
They warn that changes allowing the authorities to detain citizens without charge and censor the media during a state of emergency would violate civil liberties.