CARACAS, Venezuela — Venezuela’s all-powerful Constituent Assembly called Tuesday for a presidential election before the end of April, an accelerated schedule that seems to benefit President Nicolás Maduro’s United Socialist Party of Venezuela and put the deeply fractured and embattled opposition at a severe disadvantage.

Mr. Maduro, who came to power in 2013 after the death of Hugo Chávez, is widely expected to seek re-election even though he remains deeply unpopular amid a worsening economic crisis, rampant crime and poverty, international sanctions and the exodus of millions of Venezuelans seeking a better life abroad.

“I’m ready to be the presidential candidate,” Mr. Maduro said during a rally broadcast on state-run television.

With control of the country’s legislative system, electoral machinery and highest court, Mr. Maduro has been steering a juggernaut over the past several months, installing the Constituent Assembly over the objections of the opposition and foreign governments, and leading his party in a sweep of state and municipal elections.