(CNSNews.com) – Ahead of what could be a significant day in the Venezuelan crisis, the Maduro regime on Thursday closed the border with Brazil and said it was considering doing the same at the Colombia border, in a bid to prevent the opposition from bringing in humanitarian aid waiting in the neighboring countries.

Flanked by senior military officers, Nicolás Maduro said he was ordering the Brazil border closed “completely and absolutely” until further notice, and was also mulling “total closure of the border with Colombia.”

The Brazilian and Colombian governments are supporting the delivery of U.S. food and medicine to areas adjacent to their borders with Venezuela.

Critics attribute Venezuela’s humanitarian crisis, which has seen more than three million citizens flee in recent years, to the socialist regime’s mismanagement and corruption.

Maduro refuses to allow the aid to enter. He accuses the U.S. of using the issue as a pretext to spark a coup to install National Assembly head Juan Guaido, whom the U.S. and 50 other countries recognize as interim president pending new elections.

Guaido and supporters were making their way by convoys Thursday to the border with Colombia and the border town of Cucuta, where they hope tens of thousands of volunteers will on Saturday bring in and distribute U.S.-supplied food and medicine.

Video clips posted online purported to show flag-waving Venezuelans cheering convoys on, and National Guardsmen struggling to stop vehicles, with little evident success.

Heading to Cucuta from a different direction on Thursday was the U.S. special representative for Venezuela Elliott Abrams, leading a delegation accompanying more humanitarian supplies being flown Florida by military aircraft.

And the White House announced that Vice President Mike Pence will travel to the Colombian capital, Bogota, on Monday, “to voice the United States’ unwavering support for interim President Juan Guaido and highlight the Venezuelan people’s fight for democracy over dictatorship.”

Pence will meet with Colombian President Ivan Duque and other Western Hemisphere officials “to define concrete steps that support the Venezuelan people and a transition to democracy.”

Both the opposition and regime are gearing up for Saturday, the one-month anniversary since Guaido declared himself interim president under Venezuela’s constitution. Apart from the aid distribution efforts, rival music concerts are being planned for either side of the Venezuela-Colombia border.

“This weekend we will attempt to deliver what are now hundreds of tons of humanitarian assistance that the American people, our taxpayers, have generously paid for, now have moved into the region,” Secretary of State Mike Pompeo told NBC on Thursday. “We hope we can get it across the border.”

Asked about U.S. interests in the crisis, Pompeo pointed both to the humanitarian crisis and to security concerns.

“This is in our region,” he said. “We don’t want this to be a Cuban puppet state in Venezuela.”

Military officers urged: ‘Do the right thing’

U.S. officials continue to appeal to senior Venezuelan military officers to act in the people’s best interest in the coming days.

“You’ll ultimately be held accountable for your actions,” the commander of U.S. Southern Command, Admiral Craig Faller, said Wednesday in comments directed at the Venezuelan military. “Do the right thing. Save your people and your country.”

On Twitter Sen. Marco Rubio (R-Fla.), a vocal critic of the Maduro regime, warned Ivan Hernandez, the U.S.-sanctioned commander of Maduro’s presidential guard and military counterintelligence chief to “think very carefully about the actions you take over the next few days. Because your actions will determine how you spend the rest of your life.”

On Thursday, Hugo Carvajal, a former military intelligence head and lawmaker in the ruling socialist party, posted a video clip online pledging support for Guaido and challenging Maduro’s generals over their refusal to allow aid to enter the country.

Drawing attention to Carvajal’s defection, Rubio tweeted, “Expect more of this in the hours & days to come …”

“Threats, blackmail and coercion won’t break out unity and moral strength,” Maduro’s defense minister Vladimir Padrino Lopez said in a televised statement earlier this week. “We are not mercenaries who can be bought by the highest bidder.”