CUCUTA, Colombia (AP) -- Venezuela's National Guard fired tear gas on residents clearing a barricaded border bridge to Colombia on Saturday, heightening tensions over blocked humanitarian aid that opposition leader Juan Guaido has vowed to bring into the country despite President Nicolas Maduro's defiant refusal to accept assistance.
The opposition is calling on masses of Venezuelans to escort trucks carrying the nearly 200 metric tons of emergency food and medical supplies sent largely by the United States over the last two weeks across several border bridges.
But clashes started at dawn in the Venezuelan border town of Urena, when residents began removing yellow metal barricades and barbed wire blocking the Francisco de Paula Santander bridge. Venezuela's National Guard responded forcefully, firing tear gas on the protesters, some of them masked youth throwing rocks, who demanded that the aid pass through.
Meanwhile, Colombian migration authorities said four National Guardsmen at another crossing deserted their posts and asked for help.
There was no immediate word on their rank, but a video provided by Colombian authorities shows three of the men wading through a crowd with their assault rifles and pistols held above their heads in a sign of surrender. The young soldiers were then ordered to lay face down on the ground as migration officials urged angry onlookers to keep a safe distance.
"I've spent days thinking about this," said one of the soldiers, whose identity was not immediately known. He called on his comrades to join him in abandoning their support for Maduro's socialist government. "There is a lot of discontent inside the forces, but also lots of fear."
The potentially volatile moment for both Venezuela's government and opposition comes exactly one month after Guaido, a 35-year-old lawmaker, declared himself interim president based on a controversial reading of the constitution before a sea of cheering supporters. While he has earned popular backing and recognition from over 50 nations, he has not sealed the support of the military, whose loyalty to Maduro is crucial.
Before daybreak Saturday, national guardsmen in riot gear forced people to move away from the road leading to the Simon Bolivar bridge connecting Venezuela and Colombia. The Venezuelan government had said that it was closing three of its bridges on the border.
"We're tired. There's no work, nothing," Andreina Montanez, 31, said as she sat on a curb crying from the tear gas that was used to disperse the crowd.
A single mom, she said she lost her job as a seamstress in December and had to console her 10-year-old daughter's fears that she would be left orphaned when she decided to join Saturday's protest.
"I told her I had to go out on the streets because there's no bread," she said. "But still, these soldiers are scary. It's like they're hunting us."
Guaido and the presidents of Colombia and Chile gathered early Saturday at the Tienditas bridge where they are expected to address the media before setting out to deliver the aid loaded onto trucks.
International leaders including U.N. Secretary-General Antonio Guterres are appealing for the sides to avoid violence.
But on Friday, a member of an indigenous tribe was killed and 22 others injured in clashes with security forces who enforced Maduro's orders to keep the aid out at a crossing with Brazil.
In previous waves of unrest, citizens have been tear-gassed and killed.
Venezuelan Foreign Minister Jorge Arreaza said the military would "never have orders to fire on the civilian population" and likened the aid push to a media spectacle.
"We can only hope that sanity and good sense prevail in Cucuta, in Colombia, and that it will remain as a big show, a big party, and that they don't try to open the doors to a military intervention," he said at U.N. headquarters in New York Friday.
The push comes on the heels of a giant concert organized by British billionaire Richard Branson aimed at pressuring Maduro to accept the aid. Tens of thousands of Venezuelans gathered in a field to hear pop stars like Juanes sing beneath a scorching sun. Guaido made a surprise appearance toward the end.
"Juan arrived! Juan arrived!" people shouted as they spotted him smiling near the stage.
"Here is a Venezuela in search of freedom," he said at an aid storage facility. "Thank you, to the people of the world, for opening your doors to us."
The opposition is planning to hold three simultaneous aid pushes on Saturday. Aside from the events in Colombia, they also hope to get humanitarian assistance delivered by sea and through Venezuela's remote border with Brazil. Protests are also planned in the capital, Caracas.
Venezuela's military has served as the traditional arbiter of political disputes in the South American country and in recent weeks top leaders have pledged their unwavering loyalty to Maduro. However, many believe that lower-ranking troops who suffer from the same hardships as many other Venezuelans may be more inclined to now let the aid enter.
Opposition leaders are pushing forward in belief that whether Maduro lets the aid in or not, he will come out weakened. They also contend that if the military does allow the food and medical gear to pass, it will signify troops are now loyal to Guaido.
Analysts warn that there may be no clear victor and humanitarian groups have criticized the opposition as using the aid as a political weapon.
"I don't know that anyone can give a timeline of when the dam might break, and it's quite possible that it won't," said Eric Farnsworth of the Council of the Americas and Americas Society, a Washington-based think tank.
Fearful of what they might encounter, some Venezuelans in Cucuta said they planned to stay away from the border crossings, while others said they'd face the risks and go.
"For my son, I'd risk everything," Oscar Herrera, 25, a Venezuelan man who took an 18-hour bus ride to Colombia to buy his infant medicine for a skin irritation earlier this week.
Hernan Parcia, 32, a father of three, said he planned to go with his entire family.
"I'm pained by what's happening to my country," he said. "They can count on me."