The United States, most of Latin America, and the European Union recognize Guaido as interim president, while Russia, China, and Cuba back Maduro.
Army trucks blocking a tunnel nearly two hours west of Caracas are preventing Venezuelan National Assembly President Juan Guaido from reaching the Colombian border to oversee the entry of humanitarian aid planned for Saturday.
Maduro said he's also weighing whether to shut down the border with Colombia.
The White House said Pence will deliver remarks to the 14 nations that are part of the "Lima Group" in Bogota about addressing the humanitarian crisis in Venezuela and ongoing USA efforts to deliver aid to the country.
Guaido has said he would help volunteers transport the aid, much of it medical and food supplies from the United States, across the border near Cucuta on Saturday.
Mr Branson said he aims to raise $US100 million ($140 million) to provide food and medicine for Venezuelans, but he will have some competition.
Residents fear the planned delivery of humanitarian aid had made the already-tense city yet more fraught.
Maduro made the announcement on state TV, surrounded by military commanders before opposition leaders led by Juan Guaido vowed to bring in USA supplies of emergency food and medicine over the socialist president's objections.
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Umunna, once considered a likely Labour leader, on Monday made a public call for others to join The Independent Group. A party source said Mr Lavery had spelt out the measures being taken to deal with the "appalling abuse".
"I think they're more in the realm of rhetoric than action", Mourao said of the threats in an interview with AFP.
As Guaido's convoy left Caracas, crowds waved flags in support alongside a main highway out of the capital.
"They are committing an global crime because they are endorsing a military invasion", Maduro said of the USA, speaking Thursday on state TV flanked by his top military commanders. "I don't want to take any decision of this type, but I am evaluating it, a total closure of the border with Colombia", he said. The next morning, Guaido's supporters - all clad in white - will try to cross four bridges into Venezuela at 9am, opposition official Jose Manuel Olivares said.
Guaido still has not provided details on how the aid will come in.
Maduro's government is suspicious of the U.S. stated plan to provide humanitarian assistance to Venezuelan opposition.
Paola Quintero, an activist for Venezuelan migrants, said that while the concert has had a positive, short-term impact on Cucuta's economy, many are anxious about what might happen Saturday when thousands try to move aid across the border. Even as several million Venezuelans flee and those who remain struggle to find basic goods like food and antibiotics, Maduro denies that a crisis exists. Brazil responded by saying it is going ahead with a humanitarian airlift; the aid will be stockpiled in a border town until trucks can be sent to pick it up.
"One of the things that people may not know is that Venezuela, who's so reliant on oil exports, hardly produces any food", he told The World Today.