Venezuela President Nicolas Maduro announced on Wednesday he was breaking off diplomatic ties with the United States after Donald Trump recognized opposition leader Juan Guaido as the South American country's "interim president."

"I've decided to break diplomatic and political relations with the imperialist government of the United States," said Maduro to thousands of supporters in Caracas.

"Get out! Leave Venezuela, here there's dignity, damn it," he said, giving the U.S. delegation 72 hours to quit the country.

Guaido, the head of the opposition-controlled legislature, caused a sensation on Wednesday when he told a crowd of tens of thousands of opposition supporters that he was declaring himself "acting president."

Trump was the first foreign leader to react and threw his backing behind Guaido, describing the National Assembly as "the only legitimate branch of government duly elected by the Venezuelan people."

Speaking from a balcony at the presidential palace in Caracas, Maduro accused the U.S. government of "attempting a coup d'etat."

"The extremist policy of Donald Trump's government against Venezuela is a very serious irresponsibility, it's a very serious folly," said Maduro.

"Trying to impose a government by extra-constitutional means, we cannot accept that."

He called on Venezuela's state agencies to "close ranks" in favor of "democracy" and repeated his call for loyalty from the armed forces.

"To my command, maximum loyalty, maximum unity, maximum discipline so that we win this battle together!" said Maduro.

Meanwhile, the U.S. rejected Maduro's move to sever diplomatic ties saying he did not have the authority to do so.

"The United States maintains diplomatic relations with Venezuela and will conduct our relations with Venezuela through the government of interim President Guaido, who has invited our mission to remain in Venezuela," Secretary of State Mike Pompeo said in a statement.

"The United States does not recognize the Maduro regime as the government of Venezuela. Accordingly the United States does not consider former president Nicolas Maduro to have the legal authority to break diplomatic relations."

Pompeo, however, suggested that U.S. diplomats planned to stay put and he demanded the Venezuelan military and security forces "continue protecting ... all Venezuelan citizens, as well as U.S. and other foreign citizens in Venezuela.

"We call on all parties to refrain from measures that are inconsistent with the privileges and immunities enjoyed by members of the diplomatic community," he said.

"The United States will take appropriate actions to hold accountable anyone who endangers the safety and security of our mission and its personnel," he added.