China and Cuba, along with Russia, are staunch allies of Nicolás Maduro, whose government has been increasingly isolated after more than 50 nations, including the US and UK, have recognised his rival Juan Guaidó as the interim president.
Mr Guaidó, who leads the National Assembly – the only institution in Venezuela to be controlled by the opposition – declared himself acting president in January 2019 after the election which had returned Mr Maduro to power was widely deemed to be neither free nor fair.
Mr Maduro, who has the support of the security forces, has remained in the presidential palace and largely in control of the country, but US sanctions have left his government reliant on loans from Russia and his other remaining allies.
After Russia announced it had registered the Covid-19 vaccine, which it has named Sputnik V, Mr Maduro congratulated it on its achievement.
He also said on that he would be the first to get inoculated. “The first one to be vaccinated will be me. I’m going to get the vaccine, I’m going to set an example,” he said on 16 August.
However, speaking on Sunday, he did not say whether he would be among the 500 Venezuelan volunteers.
Venezuela has fewer than 50,000 registered cases of coronavirus and 381 deaths, a much lower toll than other countries in the region.
But immunologists say the true figure could be much higher as many Venezuelans do not get tested for fear of being stigmatised after the government blamed returning migrants for the spread of Covid-19.