While the country's poverty has soared to record levels with a lack of medicine and food, Maduro denies the humanitarian crisis exists and says the US aid efforts are part of a plot to bring down his government.
On the eve of the face-off Guaido defied a government ban on leaving the country and attended the "Venezuela Live Aid" concert organized by British billionaire Richard Branson just over the border in Colombia.
Maduro has repeatedly refused to acknowledge Venezuela's need for aid, saying it's a plot by the U.S.to seize his power.
Maduro staged a rival concert a few hundred meters away on the Venezuelan side of the bridge in Tachira.
"What do the Venezuelan people think of Donald Trump's threats?"
Separately, the administrator of the U.S. development agency USAID, Mark Green, tweeted last week that he had visited Curacao and discussed possible cooperation with the island to channel official United States aid to Venezuela.
Venezuela's National Guard has fired tear gas on residents clearing a barricaded border bridge between Venezuela and Colombia to let humanitarian aid pass through.
"They're going to face a situation where they and their families are going to have to go back to Venezuela", he said. "We have to fight".
Meanwhile, some soldiers posted on the Venezuelan border defected from Maduro's control.
However, Venezuelan security forces halted the convoys with a barrage of teargas.
Soldiers later entered the village and opened fire, killing a couple and injuring several others, they said.
The tense standoff over aid claimed its first casualties Friday as two indigenous people were killed trying to prevent troops from sealing unofficial pathways across the Brazilian border.
Rights group Penal Forum said it had recorded 29 injuries and two deaths across Venezuela in clashes with troops, though Reuters could not verify this.
Guaido said that aid would come in on Saturday regardless of any military blockade.
Humanitarian aid has become the centerpiece of the stand-off between Maduro and Guaido, the 35-year-old leader of Venezuela's National Assembly who declared himself interim president exactly one month ago Saturday.
Opposition supporters clash with Venezuela's security forces at Francisco de Paula Santander bridge on the border line between Colombia and Venezuela as seen from Cucuta, Colombia, February 23, 2019. Also in attendance were the Colombian, Chilean, and Paraguayan presidents, and the United States special representative to Venezuela, Elliott Abrams. "We are not terrorists".
He blames the country's dire situation on USA sanctions that have blocked the country from obtaining financing and have hobbled the OPEC nation's oil industry.
"For that reason, I have chose to break all political and diplomatic relations with Colombia's fascist government", he told cheering supporters. We want to work: "the people attempted to force their way through", said Viviana Meza, 29, who works in a Cucuta restaurant.
"If there is any type of violence, or if there is any type of negative reaction from the hierarchy of the Venezuela armed forces, there may also be measures that are announced by the vice president and other countries in regards to closing even further the worldwide financial circle", the official said, speaking on condition of anonymity. "We are with you".
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