Venezuelans have already voted against one attempt by Chavez to lift the constitutional restriction on unlimited re-election, when a wide-ranging package of political reforms was rejected in a 2007 referendum.

Opposition parties were emboldened by that victory over Chavez, their first since he took office in 1999, and are hopeful they can stop him again.

Polls conducted in December showed more than half of voters would vote against rule change, with about 40 per cent supporting the proposal.

Chavez was first elected in 1998.

The constitution currently bars him from running again when his term expires in 2012.

On Wednesday, Venezuela's national assembly approved a controversial constitutional amendment allowing Chavez to run again.