A “Venezuela AID Live” concert inside Colombia near the border with Venezuela on Feb. 22, 2019, aims to raise money for relief efforts to buy food and medical supplies for Venezuelans. (Raul Arboleda/AFP/Getty Images)

Food and medicine for Venezuela’s sick and famished citizens lie just beyond their reach in warehouses across the country’s borders and on islands off its coast, as a showdown approaches for getting the aid into their hands.

The United States has promised $20 million in humanitarian relief for Venezuelans. But so far, 191 metric tons of supplies that have been flown to the region since Feb. 4 are stockpiled in border towns as delivery routes by land, air and sea are blocked on the orders of Venezuelan President Nicolás Maduro.

Juan Guaidó, the opposition leader recognized by some 50 countries as the legitimate interim president, says he has lined up hundreds of thousands of volunteers to bring the material across the border on Saturday. Guaidó arrived in Colombia late Friday to participate in the convoy, defying a travel ban placed on him.

The potential for violence over boxes filled with basics such as bandages, biscuits, hand sanitizer and toothpaste grew on Friday, when the Venezuelan military fired on civilians trying to keep a road open on a stretch of the southern border with Brazil. Two civilians were reported killed.

Colombia, which has taken in more than a million Venezuelans fleeing their country’s collapsing economy, has become a base for the international resistance to Maduro. Vice President Pence will be in Bogota on Monday to deliver a speech in which he is expected to reiterate U.S. support for Guaidó.

But this weekend, attention will center on the border city of Cucuta, 350 miles north of the Colombian capital. The potential for supplies to finally get through to Venezuela has drawn diplomats, aid workers and rock stars eager to help if Guaidó’s volunteers show up.

A U.S. military C-17 cargo plane flying from Homestead Air Reserve Base in Florida landed Friday in Cucuta. It carried enough food to feed 2,000 people for a month, along with wheelchairs and crutches, and hygiene kits with soap and toothbrushes, all to be positioned near the border bridge where the Venezuelan military has placed shipping containers and trucks as roadblocks on the other side.

Elliott Abrams, the State Department’s special envoy on Venezuela, and senior officials from the U.S. Agency for International Development also flew in to oversee the operation. USAID Administrator Mark Green was at the border earlier this week.

So far, most of the U.S. aid has gone to Colombia, but the stockpiling spread to Brazil on Friday. The United States put in position 178 metric tons of food in Boa Vista, near Brazil’s border with Venezuela. The food was bought in Brazil instead of being flown from the United States, a common procedure used to save on transportation costs, move needed supplies to their destinations quickly and help local economies.

The items included kits of rice, beans, sugar and salt to feed about 3,500 people for 10 days, a U.S. official said. Additional rice is on hand to feed 6,100 people for a month.

“To save lives, this critical aid must be allowed to enter Venezuela,” the official said.

More goods donated privately are on hold in Curacao, a Dutch Caribbean island off Venezuela’s northern coast that the Netherlands has designated a “logistical hub” for aid destined for Venezuela.

Rafael Gottenger, the vice president of the Miami-based Venezuelan American Medical Association, said doctors working in Venezuela have told him of patients dying for lack of medication for diabetes, and of broken dialysis equipment and outbreaks of malaria, measles and diphtheria. He said his organization has lined up 70 Venezuelan doctors living in the United States to return to their native country to help if the government changes.

The USAID effort to get aid ready for delivery to Venezuela has involved the kind of organization the agency usually undertakes for natural disasters such as hurricanes and floods. It has used U.S. military cargo planes as well as commercial aircraft to move humanitarian aid to the Colombia-Venezuela border. It has employed local trucks to transport the supplies overland to warehouses, where it also stores items purchased locally.

According to USAID, the flights have included emergency medical kits with bandages and basic items that a person can use to attend to everyday injuries and illnesses. They have sent personal hygiene kits for 35,000 people. Food kits include nutritional supplements to treat 10,000 malnourished children for two months, and enough high-energy biscuits that can be a temporary meal replacement for 10,000 children for a month. Food kits made up of items purchased locally contain vegetable oil, flour, lentils and rice to feed 5,000 people for 10 days.

More goods have been positioned in Miami and Houston and can be dispatched if the Venezuelan government starts allowing the food through.

Once a wealthy country, Venezuela has been riven by political turmoil that has produced hyperinflation of over 1 million percent. The collapse of the economy has impoverished all but the most elite members of society, usually those with government connections.

But Maduro has opposed the aid deliveries, calling them part of a Washington-orchestrated “coup” against his government. He has said Venezuelans are not “beggars” and do not need the help.