Call it a humanitarian battle of the bands.
First, the British billionaire Richard Branson said last week that he would organize an aid concert for Venezuela this Friday night — on the Colombian side of a border bridge where urgently needed supplies are being blocked by shipping containers on the orders of Venezuela’s embattled president, Nicolás Maduro.
Then Mr. Maduro’s government said on Monday that it would stage rival concerts over the weekend on the Venezuelan side of a different border bridge, where thousands of desperate Venezuelans have recently crossed into Colombia to escape the economic and political crisis at home. Venezuelan officials also promised to deliver 20,000 boxes of government-subsidized food to Cúcuta, the Colombian city that for most of the migrants is the start of a long and uncertain journey by foot.
The rival events further complicate a tense scene at the border that may have significant implications for the future of Venezuela, where two men are claiming the presidency simultaneously.
On the Venezuelan side, there are soldiers, militiamen and missiles sent by forces loyal to Mr. Maduro, whose legitimacy was challenged in January when the opposition leader, Juan Guaidó, declared himself interim president during major antigovernment protests.
On the Colombian side, there are news camera crews and trucks full of supplies. Yet Mr. Guaidó and other opposition leaders have not explained how the aid will reach Venezuela, saying that sharing their plans would be a security risk.
On Monday, President Trump delivered his sharpest warning yet to Venezuela’s military authorities, telling a crowd in Miami that they would “lose everything” by remaining loyal to Mr. Maduro and refusing to allow in emergency aid from the United States, from Colombia and from Venezuelans abroad that has been stockpiled along the border. The Trump administration and Mr. Guaidó have declared Saturday the deadline for getting humanitarian aid into Venezuela.
Mr. Trump said members of the Venezuelan military would find “no safe harbor, no easy exit and no way out” if they did not accept Mr. Guaidó’s earlier offer of amnesty to any of them who were found not guilty of crimes against humanity. “We seek a peaceful transition of power, but all options are open,” Mr. Trump said.
Mr. Maduro, who is no longer recognized by the United States and roughly 50 other nations as the Venezuelan president, has vowed not to let the American aid enter his country. He was quoted as saying on Monday that 300 tons of aid would arrive by air from Russia two days later.
He added that his government had paid for the Russian aid shipment, along with aid from China and Turkey.
Now the dueling music events are deeply entwined in the larger battle over who has the authority to help ordinary Venezuelans deal with life-threatening shortages of food and medicine.
The goal of Mr. Branson’s event, Venezuela Aid Live, is to raise $100 million online for humanitarian aid and to “bring global attention to this unacceptable and preventable crisis,” as the event’s website says.
The A.P. reported that the lineup for Venezuela Live Aid, to be held on the blocked Tienditas International Bridge on the outskirts of Cúcuta, included the Mexican band Maná and the Dominican songwriter Juan Luis Guerra, along with the French-Spanish producer Manu Chao and the Spanish songwriter Alejandro Sanz. It quoted Mr. Branson as saying that all participating artists would perform for free.
Any international artists who accept Mr. Maduro’s invitation to perform may face harsh criticism.
Last year, a Turkish celebrity chef known as Salt Bae faced withering attacks on social media after serving Mr. Maduro an extravagant meal at his Istanbul steakhouse.
“I don’t know who this weirdo #Saltbae is, but the guy he is so proud to host is not the president of #Venezuela,” Senator Marco Rubio, the Florida Republican who has led the United States government campaign against Mr. Maduro, wrote on Twitter at the time.
The chef, whose real name is Nusret Gokce, later deleted footage from Instagram that had shown him preparing lamb chops for Mr. Maduro and his wife.
An earlier version of this article misspelled the surname of a journalist. She is Patricia Garip, not Garipa.