In a taped interview that aired on CBS News, US President Donald Trump said that military action in Venezuela against Maduro remains "an option".
In Europe, undeniably the most outspoken political leader against Maduro was Spanish Prime Minister Pedro Sanchez. Spain is one of the main destinations for migrants from Venezuela, many of whom have fled Maduro's rule and the continuing humanitarian crisis. According to United Nations statistics, as many as 208,300 Venezuelans have arrived in Spain.
In a video statement posted on Twitter, Sanchez recognised Guaido as interim leader and called for new elections "as soon as possible".
"Elections that are free, democratic, with guarantees and without exclusions, in which Venezuelans decide, with their voice and vote, their future, without fear, pressure or threats. It is, definitely, the people of Venezuela who have to decide its future."
French President Emmanuel Macron said much the same. "Venezuelans have the right to express themselves freely and democratically," he wrote on Twitter.
After British Foreign Secretary Jeremy Hunt confirmed that his country would join those backing Guaido, a spokesman for Prime Minister Theresa May said London was studying the possible sanctions.
"Venezuelan people deserve a better future. They have suffered enough, and the Maduro regime must end. It is time for free and fair elections," the spokesman told reporters, according to Reuters. "We are looking at what further steps we can take to ensure peace and democracy in Venezuela including through sanctions."
Speaking to reporters in Brussels after a meeting of European Union foreign affairs ministers, top EU diplomat Federica Mogherini said that "the EU and its member states never recognised as legitimate the presidential elections that were held last year [in Venezuela]. We did not participate, none of us, at the inauguration of Maduro on January 10. We recognise as the legitimate institution in the country the National Assembly and recognize the role of its president."
She said the European Union will take part in a meeting with South American countries in Montevideo later this week "to try to find both a democratic and peaceful solution to the crisis in Venezuela."
Mogherini added it was not up to the EU to recognise countries and their leaders, as it is a matter for EU countries to decide whether they should diplomatically recognise a nation and its leaders. However, she said that later a group of European countries would release a joint statement calling for snap elections in Venezuela and to recognise the president of the National Assembly as the interim president.
In a statement, Venezuela's Foreign Ministry rejected the announcements by European countries, charging that they were "officially joining the US' strategy to overthrow the legitimate Government of President Nicolas Maduro."
The Government, it said, will "completely revise bilateral relations with those countries from now on".
Maduro fired back personally at his international critics during a military exercise in the state of Aragua, east of Caracas. In the past week, the leader has attended numerous exercises and spoken to soldiers, likely because of the major role the military will play in determining his future.
"I call to reject intervention," he said, urging the soldiers to defend the country against "Yankee imperialism".
"The coward government of Spain has made a terrible decision in the history of relations between Spain and Venezuela. I tell Pedro Sanchez, God forbid, but if some day a coup takes place, your hands will be tainted with blood," he said. He added that "no one imposes an ultimatum on Venezuela".
The moves by European powers further isolate Maduro, who has already lost the recognition of a host of nations, including the United States, Canada, Brazil, Colombia, Argentina and Israel.
If all European countries follow in the footsteps of the Trump Administration, their decision to recognise Guaido could potentially cut the Venezuelan Government off from any accounts or assets in those countries. Already, the Bank of England has reportedly denied a request by Maduro to repatriate US$1.3 billion worth of Venezuelan gold being kept in its vaults.
"The unity of positions in the modern and most influential foreign powers leaves Maduro isolated and weakened, and it strengthens Guaido's leadership internally," said Luis Vicente Leon, a political analyst and director of the Datanalisis polling agency.
EU support, opposition leaders say, may also help break the Maduro government's narrative that Venezuela's crisis is simply a proxy war between the US and Russia.
"It marks this fight not as a fight of Trump versus Maduro or Latin America versus Maduro but a fight that is of the world against Maduro," said Julio Borges, an exiled opposition politician who has been key in building Guaido's strategy.
