Venezuelan President Hugo Chavez says he will appeal to the Supreme Court if a referendum on his rule is given the go ahead.
The opposition say 3.4m people signed the referendum petition
He accuses his opponents of "massive fraud" over the 3.4 million signatures they say they have collected.
The results of the referendum petition were delayed on Friday, with officials saying they aim to announce the results by the end of February.
Mounting tensions on the issue have spilled over into street clashes.
Violent confrontations in three cities broke the calm of recent weeks, as both sides awaited the referendum ruling.
More violence is feared after opponents of President Chavez called a big demonstration for Saturday.
Jorge Rodriguez, director of the National Electoral Council (CNE), said the council was "doing everything possible" to make its final ruling on the validity of the petition by the end of February.
He said some of the signatures had to be reappraised because personal details on petition sheets had been filled out by staff at sign-up centres, rather than the signatories themselves, according to AP news agency.
The council's three directors, including Mr Rodriguez, are themselves on opposing sides of the debate and appear to disagree about whether this constitutes a violation of the rules.
Chavez's socialist rhetoric has infuriated middle-class Venezuelans
The opposition needs to collect the verified signatures of 20% of the voting population - 2.4 million people - to trigger a referendum on Mr Chavez and other elected officials.
Mr Chavez had previously pledged to accept any decision by the electoral authority.
But on Friday he accused opponents of resorting to fraud to collect the signatures, and claimed the forms were filled out incorrectly.
At a news conference, he held up forms he claimed were "signed" by dead people, minors and foreigners.
"In the eventuality that the National Electoral Council says there will be a referendum... we would go to the Supreme Court with all this proof," he told reporters.
Clashes were reported in three Venezuelan cities on Thursday.
In Merida, west of the capital Caracas, opposition students fought with riot police, who fired tear gas and rubber bullets. Fifteen police, four students and a journalist were reportedly injured.
Pro- and anti-Chavez demonstrators clashed in Valencia, also west of Caracas. Local television showed them exchanging punches and kicks and hitting each other with sticks.
More scuffles were reported in Barcelona, in eastern Venezuela.
The violence has ruptured months of relative calm since dozens died and hundreds were injured in a 2002 attempted coup and a two-month strike last year.
There are concerns more violence might be on the way.
Opposition supporters were planning on Saturday to march to the National Electoral Council headquarters in Caracas to protest against the delays to the referendum process.
US and British authorities warned their nationals to stay away from downtown Caracas at the weekend.