CUCUTA, Colombia — The Venezuelan military has barricaded a bridge at a key border crossing, issuing a challenge Wednesday to a U.S.-backed effort by the opposition to bring humanitarian aid into the troubled nation.

The Tienditas International Bridge was blocked a day prior by the Venezuelan National Guard with a giant orange tanker, two large blue containers and makeshift fencing near the border town of Cucuta, Colombian officials said.

The bridge is at the same site where officials plan to store humanitarian aid that opposition leader Juan Guaido is vowing to deliver to Venezuela. The Trump administration has pledged $20 million in aid, and Canada has promised an additional $53 million.

The squabble is the latest front in the battle between Guaido and President Nicolas Maduro, who is vowing not to let the supplies enter the country. Maduro argues Venezuela isn’t a nation of “beggars” and has long rejected receiving humanitarian assistance, equating it to a foreign intervention.

Looking up at the giant containers blocking the bridge Wednesday, aid worker Alba Pereira shook her head and dismissed the barricade as another government ploy. She said that humanitarian volunteers would find a way to get the aid into the country.

“It’s a means of intimidation, but I don’t think it will accomplish anything,” said Pereira, director of the nonprofit Entre Dos Tierras, which aids Venezuelans migrants.

Roughly 40 countries around the world have backed Guaido, who swore himself in as president in late January contending that as head of the opposition-led National Assembly he is Venezuela’s rightful leader because Maduro’s re-election last year was a sham.

Guaido says the emergency shipment is a “test” for Venezuela’s armed forces, which will have to choose if they allow the much needed aid to pass, or if they instead obey orders. No details have been released on exactly how the opposition plans to get the shipments into Venezuela.

Soaring hyperinflation has forced millions of Venezuelans to flee or go hungry as they struggle to find or afford basic items like food and medicine.

U.S. Secretary of State Mike Pompeo said Venezuelans desperately need the emergency supplies that the U.S. and other countries are preparing to provide.

“Venezuela’s military under Maduro’s orders is blocking aid,” Pompeo tweeted. “The Maduro regime must LET THE AID REACH THE STARVING PEOPLE.”

Guaido on Wednesday accused Maduro’s government of rejecting the assistance because officials often handed out imported food and medicine in exchange for bribes.

Speaking to farmers, Guaido said the transitional government is taking steps to make Venezuela self-reliant.