The rally, to be led by Lilian Tintori, wife of jailed opposition leader Leopoldo Lopez, is the latest in more than a month of anti-government demonstrations, many of which have been countered by pro-Maduro crowds and security forces.
The death toll since April, when the protests intensified after Maduro's administration and the courts stepped up efforts to undermine the opposition, is at least 36 according to prosecutors.
The latest fatality, that of a 22-year-old man, occurred during looting in impoverished Venezuelan cities that have been hardest hit by a worsening economic crisis. In Valencia, where the man died, some areas looked like a disaster zone with bars on shop windows bent and windows broken.
Demonstrators blame Maduro for the country's plight and the penury of food and medicine. They are demanding elections to remove the leftist president.
Maduro, backed by the Venezuelan military, is resisting. He and the opposition have blamed each other of using armed groups to sow violence.
The president has started a process to rewrite the current constitution brought in under his late predecessor and mentor Hugo Chavez. The opposition and many protesters say that is a tactic to try to dodge elections.
