Washington — Representatives of National Assembly President Juan Guaidó, who has been recognized by the U.S. and more than four dozen countries as Venezuela's legitimate leader, believe the humanitarian aid being dispatched to the crisis-stricken South American nation will test the Venezuelan military's loyalty for President Nicolás Maduro.

As shipping containers block the main highways near the border with neighboring Colombia, two of Guaidó's top diplomats told CBS News the nation's armed forces will soon face a critical choice: enforce Maduro's orders to stop international humanitarian assistance — or defect and allow the aid to reach a Venezuelan population grappling with widespread food and medicine shortages.

"This will be a key moment for the military to see which side they will be on," Carlos Vecchio, Guaidó's ambassador to the U.S., told CBS News. "If they will be with the Maduro regime, which is not going anywhere … or if they will stay with the Venezuelans who need that food and medicine."

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Along with recognizing Guaidó as Venezuela's interim president and issuing sweeping sanctions against the largest state-owned oil company, the Trump administration has pledged more than $20 million in humanitarian assistance to the Venezuelan people. Food, hygiene kits and emergency medical supplies shipped by different countries are being staged in the Colombian border town of Cúcuta.

A child wearing a U.S. flag attends a gathering of Venezuelan doctors at the entrance of a warehouse where humanitarian aid for Venezuela is being stored near the Tienditas cross-border bridge between Colombia and Venezuela in Cúcuta. MARCO BELLO / REUTERS

But Maduro, who has managed to maintain a tight grip on Venezuela's armed forces, adamantly opposes assistance from nations that support Guaidó, who has called for Maduro's ouster and free elections. He has repeatedly accused the U.S. and its allies in the region of "manufacturing" a humanitarian crisis in his country and warned against American military intervention, which he has said would lead to a conflict worse than the Vietnam War.

Last week, Maduro even launched an anti-aid campaign on social media and denounced the humanitarian assistance as a "poison of humiliation."

In an interview with CBS News partner network BBC News, Maduro called President Trump a white supremacist and accused the "U.S. empire" of waging a "political war" against Venezuela. He acknowledged that his country has "problems," but the embattled leader said hunger was not one of them, casting the international aid efforts as a ploy to "humiliate" the Venezuelan people.

"This is part of that charade," Maduro said. "That's why, with all dignity, we tell them we don't want their crumbs, their toxic food, their left-overs. We tell them 'no, Venezuela has dignity, Venezuela produces and works and our people do not to beg from anyone.'"

Gustavo Tarre, Guaidó's representative to the Organization of American States (OAS), said Maduro is reluctant to allow the foreign assistance into the country because it would make him and his regime look weak.

"It is an incredible thing that you have a president who has not created the conditions in order for the people to eat and to have the drugs they need when they're ill, but he doesn't accept the foreign aid," Tarre told CBS News "An acceptation of a crisis is an acceptation of a failure of government."

Tarre added that the critical moment will come if and when supplies start flowing across the border. High-ranking military officials will have to decide whether to follow orders or allow the desperately-needed supplies to enter the country.

"If they are the normal guards, I'm sure they won't open fire, but if they have the people motivated by the government, that's the risk," Tarre said. "But we still think that if you have hundreds of thousands of people behind waiting for food … they are going to allow the trucks to pass."

Oil-rich Venezuela was once considered one of Latin America's wealthiest nations. But under Maduro — who in 2013 replaced the late Hugo Chavez, another leftist firebrand accused of consolidating power — economic turmoil, skyrocketing inflation, food and medicine shortages, mounting crime and government corruption have plunged the country deep into a socio-political crisis.

To stifle discontent over the floundering economy, weakened further by international sanctions and plummeting oil production, Maduro has resorted to political oppression and reportedly, even torture. Recent elections in the country have been denounced by United States and the international community as unfair and rigged.

The dire situation has prompted more than 2.3 million Venezuelans to flee the country since 2014 — an exodus Human Rights Watch called "the largest migration crisis of its kind in recent Latin American history." More than one million Venezuelans have fled to Colombia, hundreds of thousands to Peru, Ecuador and other countries in the region and more than 72,000 have come to the U.S.

With many poor Venezuelans going hungry, Guaidó is hoping the international humanitarian aid he has enthusiastically welcomed erodes pro-government loyalty in working-class neighborhoods, which have historically been bastions of support for Maduro's socialist agenda.

The State Department's special representative to Venezuela Elliot Abrams said "it's probably correct" that the military "could prevent international aid from reaching Venezuela."

"That would be a really tragic situation," he added. "And we are hopeful that that won't happen."