Some 200 police blocked hundreds of opposition demonstrators shouting "Recall now" as they tried to march on the headquarters of the National Electoral Council (CNE) in Caracas.
There were no clashes, but the muscular police response lay bare the tension gripping the country as it lurches through an economic crisis that is causing severe food shortages and hyperinflation.
"The government is desperate. They're afraid of the people's vote. They'll use every trick they can" to avoid a recall, said the speaker of the opposition-majority legislature, Henry Ramos Allup.
But the leftist leader's camp made clear it was not going without a fight on Tuesday, when it asked the electoral authority to ban the opposition coalition, the Democratic Unity Roundtable (MUD).
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The move came just as the opposition was hoping to get a green light to proceed to the next stage of the lengthy referendum process.
A top Maduro aide instead accused the opposition of committing "gigantic fraud" by allegedly including the names of thousands of dead people, convicts and minors in a petition submitted in May with 1.8 million signatures requesting a recall vote.
"But they could be useful (to Maduro's camp) as a political strategy to delay the recall referendum process. The deadlines are starting to get dangerously close," he told AFP.
Maduro's opponents are racing to force a recall vote by January 10, the cutoff to trigger new elections.
After that date -- four years into the president's six-year term -- a successful recall vote would simply transfer power to Maduro's hand-picked vice president.
Tuesday was the final day for electoral authorities to rule whether the opposition successfully collected at least 200,000 valid signatures, the first stage of the process.