The US has rejected a move by Venezuela’s Nicolas Maduro to break diplomatic ties, saying it does not think he has the authority to make the call.

Instead, the US says it will conduct relations with a government led by Venezuelan opposition leader Juan Guaido.

“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 on Wednesday (US time).

“The United States does not recognise 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.”

Mr Guaido declared himself interim president of Venezuela on Wednesday, winning the backing of Washington and many Latin American nations. That prompted Mr Maduro, who has led the oil-rich nation since 2013, to break relations with the US and to give American diplomats 72 hours to leave the country.

Mr Pompeo, however, suggested that US diplomats planned to stay put. He demanded the Venezuelan military and security forces “continue protecting … all Venezuelan citizens, as well as US 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.”

Earlier, US President Donald Trump said he backed Mr Guaido as the Venezuela’s leader, labelling the embattled Maduro government “illegitimate”. The move, which was followed by Canada, came as mass street protests continued across Venezuela.

“I will continue to use the full weight of United States economic and diplomatic power to press for the restoration of Venezuelan democracy,” Mr Trump said.

There have been mass protests across Venezuela against Mr Maduro. Photo: Getty

A senior US official, speaking on condition of anonymity, warned Mr Maduro and his loyalists that Washington was ready to increase oil, gold and other sanctions and take unspecified actions “if they choose to harm any of the national assembly members or any of the other duly legitimate officials of the government of Venezuela”.

Asked whether he was considering US military intervention in Venezuela, Mr Trump later said: “All options are on the table.”

Venezuelan opposition sympathisers had been urging Mr Guaido to assume the presidency since Mr Maduro was inaugurated for a second term on January 10. That followed a widely boycotted election last year that the US and many other foreign governments characterised as fraudulent.

Mr Guaido, 35, has energised the opposition with a campaign to declare Mr Maduro a usurper. He has promised a transition to a new government in a nation suffering a hyperinflationary economic collapse.

Mr Guaido, a newcomer on the Venezuelan national scene who was elected to head Congress on January 5, had said earlier he was willing to replace Mr Maduro if he had the military’s support, with the aim of then calling for free elections.

US recognition of Mr Guaido could backfire if Mr Maduro uses it as a pretext to take action such as detaining him or other opposition figures.

Adding to pressure on Mr Maduro, multiple sources said the Trump administration could impose new US sanctions on Venezuela’s oil industry as soon as this week if the political situation there deteriorates further.

-with AAP