Hundreds of thousands of Venezuelans are expected to join a march on Wednesday in a bid to topple President Nicolás Maduro’s government.
The protests will mark 61 years since the fall of the country’s military dictatorship in 1958.
National Assembly president Juan Guaidó, who has organised the demonstration, called it a “historic appointment with the people”.
US Vice-President Mike Pence meanwhile has signalled his support.
In an opinion piece for the Wall Street Journal, Mr Pence said the US “strongly supports the National Assembly and Mr Guaidó”.
“Nicolás Maduro has no legitimate claim to power,” he wrote. “Nicolás Maduro must go.”
Venezuelan Vice-President Delcy Rodriguez dismissed Mr Pence’s intervention, reportedly telling a news conference “Yankee go home”.
The opposition protest aims to back an attempt by Mr Guaidó to establish a transitional administration ahead of new elections.
The governing Socialist Party has announced a rival protest to counter the opposition march.
Wednesday’s demonstrations come just two days after 27 National Guard soldiers allegedly revolted against the government at a guard post in the capital, Caracas.
Anti-government protests erupted in the neighbourhood where
Government officials dismissed it as a cover to steal weapons.
Addressing soldiers on Monday, Mr Guaidó promised amnesty for those who refused to serve the government.
“We’re not asking you to launch a coup d’état, we’re not asking you to shoot,” he said. “We’re asking you not to shoot at us.”
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Mr Guaidó called for demonstrations after Mr Maduro was sworn in for a second presidential term this month.
He was re-elected in a May 2018 vote boycotted by the opposition and condemned by many in the international community.
Mr Guaidó wants to replace Mr Maduro and serve as an interim president ahead of elections.
Venezuela’s Supreme Court on Tuesday asked the state prosecutor to investigate whether Mr Guaidó had committed a crime.
Millions have fled Venezuela in recent years amid a deepening economic crisis brought on by a drop in the price of oil in 2014.