Guaido is organizing two marches that will depart from two locations at 9 a.m. local time in Caracas. He is demanding that Maduro step down and for new elections to be organized.
Students and other youth organizations in Caracas and several cities across the country are also organizing protests. It is the third large march called by Guaido this year.
Elvis Amoroso, the comptroller designated by the National Constituent Assembly, a special Parliament to oversee matters related to the Constitution, has asked for an investigation of Guaido's personal wealth, El Nacional reported. The National Constituent Assembly was not elected in a process considered valid, as the opposition did not participate.
Amoroso said Guaido is suspected of having declared false information and of receiving funds from national and international organizations.
The United States and other countries have said they recognize Guaido as legitimate leader.
Meanwhile, a report by Russian news agency Tass said that Venezuelan state PDVSA has longstanding accounts with the Gazprombank Group.
The report came after media reported that PDVSA is telling clients to make payments to the company through a Gazprombank account.
The United States last week sanctioned PDVSA by banning any U.S. company that buys Venezuelan crude oil from making payments to accounts to which Maduro has access. The United States has also closed its financial system to transactions involving Venezuelan gold.
The United States is trying to increase pressure to support Guaido, who earlier this year said he was assuming the Venezuela presidency after the National Assembly, the only legally elected parliament, had declared Maduro's second presidential term, which started Jan. 10, illegal.
Maduro's second term was declared illegal on grounds his 2018 re-election was not valid. Nearly all of the opposition did not participate in 2018 elections, claiming it was not a free process.
Countries including most big nations in Latin America, the United States, Canada, some Baltic and European nations support Guaido. However, countries including Russia, China, Cuba, North Korea support Maduro.
Guaido asked for international aid, which is being collected in Cucuta, Colombia, near the Venezuelan border. Maduro's security forces have said they declined such aid and blocked one international bridge to prevent the aid from going through.