"We denounce the illegitimate former Venezuelan Attorney General's threats against President Juan Guaido", Bolton said via Twitter. "Let me reiterate — there will be serious consequences for those who attempt to subvert democracy and harm Guaido".
Earlier, Venezuela's Prosecutor General Tarek Saab announced his intention to conduct an investigation into Guaido and asked the Supreme Court to implement a travel ban. Guaido proclaimed last week himself the interim president of the country and was swiftly recognized by Washington and its allies.
On Monday, Bolton during a press conference announced that the United States was imposing sanctions on Venezuelan oil company PDVSA. US Treasury Secretary Steven Mnuchin said PDVSA could be relieved from US sanctions if it commits to the expeditious transfer of control to Guaido.
Maduro on Monday accused the United States of an attempt to "steal" the US-based Citgo energy company, a subsidiary of Venezuelan state-owned PDVSA oil and gas company, and called the new US sanctions against PDVSA illegal.
Maduro, the twice democratically elected president, has called the opposition leader a "US puppet", accused Washington of attempting to organize a coup in Venezuela and declared his intent to cut off diplomatic ties with the US.
Earlier in the day, State Department spokesperson Robert Palladino confirmed in a statement that US Secretary of State Michael Pompeo has certified the authority for Juan Guaido to take control of some Venezuelan government assets.