The United States on Tuesday threw its full weight behind Venezuela's self-proclaimed acting president Juan Guaido, as the opposition leader said troops had joined his campaign to oust President Nicolas Maduro.
"Today interim President Juan Guaido announced start of Operacion Libertad," or "Operation Freedom," tweeted Secretary of State Mike Pompeo, as Maduro's government vowed to put down what it called an attempted coup.
"The U.S. Government fully supports the Venezuelan people in their quest for freedom and democracy. Democracy cannot be defeated," Pompeo wrote.
Earlier, the White House urged Venezuela's armed forces to stand by the country's "legitimate institutions."
"@vladimirpadrino: The FANB must protect the Constitution and the Venezuelan people," tweeted National Security Advisor John Bolton, addressing the country's Defense Minister Vladimir Padrino Lopez.
"It should stand by the National Assembly and the legitimate institutions against the usurpation of democracy. The United States stands with the people of Venezuela."
President Donald Trump's administration has been waging a mounting pressure campaign to oust Maduro and install Guaido, who is recognized as acting president by more than 50 countries, including most in Latin America.
Re-elected in a vote widely condemned for irregularities, Maduro presides over a crumbling economy, with inflation forecast to hit a mind-boggling 10 million percent this year and millions of Venezuelans having fled due to shortages of basic goods.
He has so far survived three months of US-led pressure, including efforts to deprive him of Venezuela's financial lifeline of oil sales, and still enjoys critical backing from Russia and China.
Guaido has vowed that protests on Wednesday for the May 1 workers' holiday will be the biggest in Venezuela's history, heightening fears that the crisis will turn violent.
The State Department in a travel alert advised US citizens in Venezuela to take shelter in the coming days if they cannot leave the country.