The United States has slapped sanctions on the state-owned Venezuelan oil company Petroleos de Venezuela (PDVSA), saying it is one of the entities responsible for the country's "tragic decline".
The company "has long been a vehicle for corruption", the US Treasury says, citing schemes designed to embezzle billions of dollars "for the personal gain of corrupt Venezuelan officials and businessmen".
Petroleos is a primary source of Venezuela's income and foreign currency.
Treasury Secretary Steve Mnuchin told reporters at the White House on Monday the action was meant to intensify pressure on President Nicolas Maduro.
"The United States is holding accountable those responsible for Venezuela's tragic decline and will continue to use the full suite of its diplomatic and economic tools to support interim president Juan Guaido, the National Assembly and the Venezuelan people's efforts to restore their democracy," Mnuchin said.
National Security Adviser John Bolton joined Mnuchin at the briefing, saying more than 20 other countries have followed the US decision to no longer recognise Maduro as president.
Bolton says the action is a statement backing the people of Venezuela, who he says "have had enough of oppression and economic hardship".
The news came as Guaido announced he had ordered congress to begin the process of naming new boards of directors to PDVSA and US refining subsidiary Citgo.
The assembly will also gradually take control over Venezuelan assets abroad and take measures to guarantee transparency in the use of state resources, Guaido said in a statement.
The goal is to prevent President Nicolas Maduro and his entourage continuing "to steal the money of Venezuelans", Guaido said.
