Britain and other European powers have announced they are recognising opposition leader Juan Guaido as the interim president of Venezuela.
The move follows the failure of the embattled incumbent Nicolas Maduro to call new presidential elections as has been demanded by foreign nations.
Foreign Secretary Jeremy Hunt said the people of Venezuela had suffered enough and it was time for a “new start”, with free and fair elections in line with international democratic norms.
Spain, Germany, France, Portugal, Sweden, Denmark, Austria, the Netherlands and Lithuania all joined in recognising Mr Guaido, who proclaimed himself interim president on 23 January.
Mr Maduro, however, showed no signs of bowing to the pressure, warning that he could not rule out civil war if the protests against his regime continued.
“I don’t accept ultimatums from anybody. Why should the EU be giving ultimatums to a country?” he said in an interview with Spanish television.
In a statement, Mr Hunt said: “The United Kingdom now recognises Juan Guaido as the constitutional interim president of Venezuela, until credible presidential elections can be held.
“The people of Venezuela have suffered enough. It is time for a new start, with free and fair elections in accordance with international democratic standards.
“The oppression of the illegitimate, kleptocratic Maduro regime must end. Those who continue to violate the human rights of ordinary Venezuelans under an illegitimate regime will be called to account. The Venezuelan people deserve a better future.”
A spokesman for Prime Minister Theresa May said: “Those who continue to violate the human rights of ordinary Venezuelans under an illegitimate regime will be called to account.
“We are looking at what further steps we can take to ensure peace and democracy in Venezuela, including through sanctions.”
The spokesman declined to say what form any sanctions might take. While the UK remains a member of the European Union any such actions would be implemented at an EU level.
Mr Guaido has argued that Mr Maduro’s re-election last May was fraudulent and the constitution gave him power to declare himself interim president.
However, Labour leader Jeremy Corbyn – a long-standing admirer of Mr Maduro’s socialist predecessor Hugo Chavez – has strongly condemned outside interference in Venezuela “whether from the US or anywhere else”.