For the last year, Guaido has led opposition to Venezuela's socialist president Nicolas Maduro.
Last January, Guaido declared himself acting president - a move quickly supported by more than 50 countries - after parliament officially branded Maduro a "usurper" over his 2018 re-election, which was widely denounced as fraudulent.
Despite intense pressure from the opposition and the United States - which has imposed sanctions on regime figures - Maduro has retained power, thanks largely to support from the armed forces.
The National Assembly is the only branch of government in opposition hands. But it has been sidelined since 2017, when the Supreme Court, made up of Maduro loyalists, declared it in contempt. The court has since annulled its every decision.
The parliament session was due to begin at 11:00 am (1500 GMT.) Journalists as well as lawmakers were prevented from accessing the site.
AFP journalists saw police and army blockades in the streets surrounding the assembly building in the capital Caracas.
"The regime is kidnapping and persecuting deputies, militarizing the Federal Legislative Palace, preventing access and blocking entry to the free press," Guaido said on Twitter.
"This is the reality in Venezuela: the desire for change in the face of a dictatorship that continues to persecute."
The national press workers union launched a "worldwide alert in the face of the Nicolas Maduro regime initiative to block the press" from reaching parliament.