While intermittent outages have become regular occurrences in Venezuela of late, rarely have so many states simultaneously been without power for such an extended period.
Washington this week revoked the US visas of senior Venezuelan officials and said on Wednesday it had identified efforts by Maduro to work with foreign banks to move and hide money. Sabotage is burning food and medicine. The country's electric energy minister, for his part, said that "deliberate sabotage" on behalf of the US-backed opposition was the reason.
Humanitarian aid trucks went up in flames last month when Maduro deployed troops at the Colombian border to prevent the opposition from bringing in relief supplies.
"They're planning to tire us out, but they no longer have a way of containing the people, who have chose to ensure the end of the usurpation", Guaido tweeted on Saturday.
As Venezuela is still reeling from a nationwide blackout, Nicolas Maduro's government says the emergency was the result of an external influence. The United States in January levied crippling oil industry sanctions meant to starve Maduro's government of revenue. "There's already enough of such lessons from history, and the same old disastrous road should not be followed".
Members of the Venezuelan Bolivarian militia, supporters of President Nicolas Maduro, demonstrate in Caracas on Saturday. Venezuela can still contest the award.
By early Friday afternoon, residents and pro-government state broadcaster VTV reported that power was returning to parts of Caracas.
The entire nation was affected by the blackout. State oil company PDVSA did not respond to a request for comment. Many people said they expected they would have to walk several hours to their homes because the few buses on the streets were full and the city's metro system was shut down. Many did not realize the workday was suspended because they could not watch television or listen to the news.
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In the upscale Caracas neighbourhood of Los Palos Grandes, several hundred people gathered for a rally where Guaido was expected to speak. "Today will be a lost day for me".
"Tomorrow, I call on the Venezuelan people to make a huge statement in the streets against the usurper, corrupt and incapable regime that has plunged our country into darkness", Guaido wrote on Twitter.
The opposition has set protests for Saturday in the capital as it seeks to maintain pressure on Maduro to step down.
The United States and about 50 other countries back Guaido's contention that he is the interim president of Venezuela, and that Maduro's re-election a year ago was illegitimate because major opposition leaders were barred from running.
He has been recognised as interim president by more than 50 countries but Mr Maduro retains the support of his close allies Russia, Cuba and China, among others.
It comes following protests and rising tensions in the country to remove Maduro from power - which is being backed by the United States and other Latin American countries. Maduro has consistently attributed major power outages to sabotage by opposition adversaries, without providing evidence.
The agency says the blackout stems from an attack on the Guri power plant and that officials are working to restore service.