Guaido had earlier expressed fears of being abducted by government agents following a request by the Supreme Court to the Constituent Assembly to lift his parliamentary immunity
Venezuela's Constituent Assembly, an all-powerful legislature controlled by the ruling Socialist Party, on Tuesday approved a measure allowing for a trial of opposition leader Juan Guaido, in what appeared to be step toward having him arrested.
Guaido, leader of the opposition-controlled National Assembly, in January invoked the country's constitution to assume the interim presidency after declaring President Nicolas Maduro's 2018 re-election a fraud.
He has been recognized by the United States and most other Western nations as Venezuela's legitimate leader, and has said he does not recognize decisions emanating from the Maduro government.
The Constituent Assembly's decree is necessary for the Supreme Court to move ahead with a trial of Guaido because as a legislator he has parliamentary immunity that makes it more difficult for him to be tried than the average citizen.
"This formally authorizes the continuation of the trial of Guaido," said Constituent Assembly Chief Diosdado Cabello, who is also the Vice President of the Socialist Party.
The Supreme Court on Monday had reiterated a previous measure blocking Guaido from leaving the country, an order which he openly violated in February when he embarked on a tour of Latin American nations to bolster support for his campaign to oust Venezuelan President Nicolas Maduro.
Venezuela's chief prosecutor's office has opened an investigation of Guaido, into alleged links to "incidents of violence" in January, but has not ordered his detention or officially charged him with any crime.
"We are not going to evade our responsibility," Guaido told reporters in eastern Caracas after the announcement. "They thought this would be easy. But it won't be. If they want to move forward, they will have to assume the consequences."
Constitutional lawyer Jose Vicente Haro called the decision a "constitutional fraud" that stripped Guaido of parliamentary immunity without the approval of the legislature, which under the constitution must approve such a decision.
The legislature is currently control by the opposition.
"It also violated due process, because he should have had a hearing to defend himself," said Haro in a telephone interview.
Maduro has said Guaido should "face justice" and calls him a coup-mongering puppet for the United States - but he has stopped short of calling for his arrest.
Guaido's international backers, chiefly the Trump administration, have warned Venezuelan authorities not to touch him and threatened ever harsher sanctions against the Maduro administration to further cut it off from foreign financing.