A Constituent Assembly can rewrite the country's constitution, and many observers see the move as an attempt to strengthen the current regime's hold on power.
Senior White House officials told Reuters last month the Trump administration was considering sanctions on Venezuela's vital energy sector, including state oil company PDVSA, a major escalation in USA efforts to pressure the country's government amid a crackdown on the opposition.
After an opposition-organized referendum led some 7.2 million people in Venezuela to express their rejection of the national government, the Vatican's Secretary of State once again voiced his support for the local bishops, condemning the siege of which a cardinal was victim.
The U.S. statement was a repudiation of Maduro's planned National Constituent Assembly (ANC), which would rewrite the Constitution.
"I'm on strike "in my heart" because if we don't turn up, they will fire us", said a 51-year-old engineer at state steel plant Sidor in southern Bolivar state, waiting at dawn for transport provided by her company.
Geoff Thale, with the lobbying group Washington Office on Latin America (WOLA), told AFP he was "very skeptical that unilateral U.S. sanctions (would be) effective".
"The government jails the people who protest and those who are protesting are caging the rest of us".
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A more powerful and risky weapon is cutting back on USA imports of Venezuelan oil. There is no way to apply economic sanctions now in Venezuela without making the humanitarian situation much worse.
"I strongly and categorically reject the declarations and position taken up by the ex-official at our mission", Ramirez, the formerly powerful head of Venezuela's oil company, tweeted.
In defense of the assembly, Maduro recounted the Battle of Ayacucho in Peru, a concluding military victory of the Latin American revolutionary wars, when the forces of Grand Marshal Antonio Jose de Sucre decisively forced the Spanish Empire to surrender and end its reign over South America. The United States has always been accused of interventionism - even "imperialism" - in what Washington has sometimes viewed as its "backyard".
Maduro chaired a meeting of his Defense Council on Tuesday to prepare responses to the threatened U.S. action.
Venezuelan Foreign Minister Samuel Moncada, repudiated the White House statement at a press conference.
"Obviously the United States government is used to humiliating other nations through its worldwide relations and thinks it is going to get the subordination it is accustomed to", Xinhua news agency quoted the Venezuelan Foreign Ministry as saying.
The White House officials who briefed reporters on Tuesday seemed aware of the potential impact USA economic sanctions could have on American business.
US President Donald Trump has threatened "swift economic actions" against Venezuela if that election happens.