SAO PAULO, Brazil — Venezuelan opposition leader Juan Guaidó vowed Thursday to return to his crisis-ridden country “in the next few days,” even as he said he and his family have been the target of threats from the government of President Nicolás Maduro.

Guaidó visited Brazil on Thursday as he prepared for one of the most momentous decisions of his career — how to return to his country without facing arrest and the potential collapse of his campaign to oust the government.

Guaidó, whose claim on the Venezuelan presidency has been recognized by more than 50 other nations, traveled to neighboring Colombia last Friday, defying a court order prohibiting him from leaving the country. Opposition leaders had hoped the next day would be a turning point in Venezuela’s political drama, with the military forced to allow in international humanitarian aid stationed at the borders. Instead, the armed forces largely stayed loyal to Maduro. Guaidó has since broached the possibility of enlisting outside military help to oust the sitting Venezuelan president.

Maduro, in turn, suggested that Guaidó would be arrested if he returned to Venezuela. “He will have to face justice, and justice prohibited him from leaving the country,” he said in an interview with ABC News that aired Wednesday.

The Trump administration, a staunch supporter of Guaidó, announced Thursday that it had sent more aid via plane to the city of Cúcuta, on the Colombian border with Venezuela. The supplies “will be pre-positioned for the people of #Venezuela,” Mark Green, administrator of the U.S. Agency for International Development, said in a tweet. However, it was not clear how the aid would enter the country. Venezuelan authorities have blocked land entrances and broken relations with Colombia.

Guaidó’s visit to Brazil comes as the Venezuelan opposition is at a crossroads. In the weeks after Guaidó declared himself president on Jan. 23, citing massive fraud in Maduro’s reelection, the former National Assembly president appeared to steadily gain momentum in his bid to replace Maduro. The United States and many other countries recognized him as the Venezuelan leader, and the Trump administration announced crippling sanctions on Venezuelan oil exports, the economic lifeblood of the South American country.

But the opposition’s inability to crack the military’s support for Maduro — vividly demonstrated on Saturday — has left them struggling to find a way forward.

On Thursday, Guaidó met with Brazilian President Jair Bolsonaro, who has been a strong supporter. Guaidó is scheduled to visit Paraguay on Friday. He has not specified when he will return to Venezuela, but said at one point during his news conference in Brazil that he would be back by Monday.

Dimitris Pantoulas, a political analyst in Caracas, Venezuela’s capital, said that Guaidó had apparently expected to return as a liberator last weekend as humanitarian aid poured into the country — but was now facing a complicated decision on how to get back in. “The more time that Guaidó spends abroad, the more the opposition loses,” he said, adding that Guaidó’s absence “provides oxygen to Maduro.”

If Guaidó returns home only to be arrested, the opposition’s campaign — which has brought thousands of Venezuelans into the streets in recent weeks — could be stopped in its tracks. But if he remains abroad, the effort could also falter.

Antonio Ledezma, an exiled opposition leader who is helping to formulate Guaidó’s strategy, said the young politician was determined to return. His strategy, he said, would be to continue building bridges with military leaders and organizing demonstrations. “The possibility of a government in exile is something we have discussed, but it’s a chapter we closed,” Ledezma said.

Analysts said Guaido’s return also could be complicated for Maduro — if Guaido’s international and domestic supporters make clear they won’t tolerate his being detained.

“When Guaidó decides to return, Maduro faces a dilemma: capture him or let him enter. The cost is much higher for Maduro if he detains him than if he lets him in. Everyone would see this as a dictator making a prisoner of the other president of the country,” said Pantoulas.

Guaidó had floated the idea of international military intervention in recent days, but the idea has not been embraced by Brazil, the United States or other allies — although the Trump administration has said all options remain on the table.

On Thursday, Colombia released images of Venezuelan bulldozers pouring dirt into shipping containers that Venezuelan authorities had used to block one border bridge. Additional barricades appeared on other bridges, including one where two burned-out trucks remained. They were destroyed while trying to carry aid across the border during explosive protests Saturday.

The blocked border has not stopped the exodus of Venezuelans from a country suffering a severe economic breakdown.

“Everyone just goes through the trochas,” said Luisiris Moren, a 22-year-old Venezuelan, referring to the hundreds of illicit paths that cross the border here.

After she and her family from the Venezuelan city of Valencia arrived by bus Wednesday evening in San Antonio, on the border, they followed a stream of people down a dirt path and crossed a shallow river into Colombian territory.

The huge flow of people that once crossed these bridges daily has been diverted to a multitude of unofficial paths, challenging Colombia’s efforts to document the thousands of Venezuelans who migrate each day.

Christian Kruger, director of Colombia’s migration authority, said in the days before the border closure that Colombian authorities had tallied about 40,000 people crossing into Colombia daily and 35,000 leaving, suggesting that 5,000 people stayed in Colombia each day. With the official border crossings closed, there will be no good way to track the migration.

Krygier and Sheridan reported from Caracas. Dylan Baddour in Cúcuta contributed to this report.