The UK, Spain and other European countries have officially recognised opposition leader Juan Guaidó as interim president of Venezuela.
It comes after Pesident Nicolás Maduro defiantly rejected the EU’s Sunday deadline to call snap elections.
French Foreign Minister Jean-Yves Le Drian said Mr Guaidó had the “legitimacy” to organise a fresh presidential vote.
Mr Guaidó declared himself interim leader last month and won US backing.
Embattled president Mr Maduro accuses him of organising a coup. He said he cannot rule out the possibility of civil war as pressure mounts on him to stand down,
In a TV interview, he warned that US President Donald Trump would leave the White House “stained with blood” if he intervened in the crisis.
Mr Guaidó said on Sunday he would build an international coalition to deliver humanitarian aid to Venezuelans.
Mr Maduro responded to the EU’s deadline saying: “We don’t accept ultimatums from anyone. It’s like if I told the European Union: ‘I give you seven days to recognise the Republic of Catalonia, and if you don’t, we are going to take measures’.
“No, international politics can’t be based on ultimatums. That was the era of empires and colonies.”
Reports indicate that during an interview broadcast on Sunday, Mr Maduro was asked if the crisis in Venezuela could result in civil war.
“Today no-one could answer that question with certainty,” he said.