Juan Guaido, 35, assumes the presidency of a National Assembly stripped of power by Maduro, whose government is blamed for leading the once-wealthy oil nation into a historic political and humanitarian crisis.
Speaking to legislators, Guaido named off several opposition politicians and opponents of Maduro's government who have been jailed, driven into exile or killed. He said desperation has forced masses of citizens to flee abroad looking for work.
"We are under an oppressive system," he said. "It's not just that — it is miserable." Tall and youthful, Guaido represents the next generation of Venezuelan political opposition, taking up the assembly's leadership following 74-year-old Omar Barboza.
Guaido is an industrial engineer and former student leader from the same political party as Leopoldo Lopez, Venezuela's most popular opposition leader under house arrest. Government opponents consider him a political prisoner.
Guaido called Maduro a dictator whose legitimacy has run out. Venezuela is living a "dark but transitional" moment of its history, he said, adding that among its first acts congress will create a transitional body to restore constitutional order, but he offered no details.
He addressed a hall filled only with opposition lawmakers as the government loyalists have long boycotted any sessions, saying the National Assembly has itself overstepped its authority. However, roughly 20 foreign diplomats from the United States, Canada, Japan, Italy and Germany attended the assembly's inaugural session in a show of solidarity.
"The National Assembly should inspire hope in the Venezuelan people for a peaceful, prosperous, and democratic future, even as the corrupt and authoritarian Maduro regime and its allies seek to deny Venezuelans that right," the State Department said in a statement. It added: "Every nation must take strong action to help the Venezuelan people reclaim their democracy."
The assembly opened days before Maduro's inauguration to a second, six-year term widely condemned as illegitimate after he declared victory in the May 20 election that many foreign powers considered a sham.
Venezuela's socialist party boss Diosdado Cabello said Saturday that Maduro will be sworn in on Jan. 10 before the Supreme Court, which is stacked with government loyalists. This defies the constitution that requires a president take the oath before the National Assembly.
As international pressure mounts, a dozen Latin American countries and Canada on Friday urged Maduro to cede power and hand it over to congress until a valid president is elected. Venezuelan officials accuse the coalition of taking orders directly from U.S. President Donald Trump, who they frequently accuse of spearheading an economic war against Venezuela.
"Those of us here are fighting every day to restore democracy," Guaido said. "We want the protection of the rule of law. We want the Venezuelans to be protected, because we believe in life."