President Nicolas Maduro ordered the closure of Venezuela’s border with Brazil on Thursday in an increasingly fraught power struggle with Juan Guaido, the opposition leader spearheading efforts to bring humanitarian aid into the country despite a military blockade.

Guaido set out in a convoy of vehicles to personally pick up US aid being stockpiled on the other side of the Colombian border, defying Maduro’s military to stop him.

Recognised as interim president by more than 50 countries, he left the capital Caracas for the Colombian border in a convoy of several vehicles for the 900 kilometer trip.

Embattled Maduro has dismissed Guaido’s humanitarian caravan as a “cheap show” and slammed aid as a precursor for a US military intervention in the oil-rich but crippled Latin American country.

The 35-year-old leader of the Venezuelan legislature proclaimed himself acting president on January 23 and wants to oust Maduro, set up a transitional government and hold new elections.

A separate caravan of buses and trucks containing opposition lawmakers had earlier left eastern Caracas bound for the border.

Several of the trucks were stopped by security forces and their drivers forced to get out, but the rest of the caravan was allowed to continue, lawmakers said.

“We know that the regime is going to put all obstacles to prevent us from reaching the border, but nothing is stopping us, we are going to continue,” said opposition lawmaker Yanet Fermin.

Guaido scored important symbolic boosts Thursday as 11 Venezuelan diplomats based in the US declared their support for him.

Hugo Carvajal, a retired general and former military intelligence chief to Hugo Chavez, also recognized the opposition leader and called upon the armed forces to break from Maduro.

Signaling his growing disquiet, Maduro announced Thursday that the border with Brazil – which along with Colombia is one of the main potential avenues for aid delivery – would be “completely and absolutely” closed from 8:00 pm until further notice.

Maduro also warned Thursday he was considering “a total closure of the border with Colombia” to Venezuela’s west.

He has already ordered the military to barricade a major border bridge to prevent supplies from entering the country from Cucuta, Colombia, where tons of humanitarian aid are being stockpiled, most of it from the United States.

Meanwhile, Maduro, mirroring Guaido’s move in an attempt to show his socialist government was able to look after its people ordered a shipment of thousands of food boxes to be distributed to the needy along the Colombian border.

He also announced on Thursday the arrival of another 7.5 tons of medicine and medical supplies from Russia.

Shipments of food and medicine for the crisis-stricken population have become a key focus of the power struggle between Maduro and Guaido.

Guaido, who says 300 000 people could die without an influx of aid, says he aims to rally a million volunteers to start bringing it in by Saturday.

It remained unclear how he proposed to do so if the blockade continues but experts have pointed to the notoriously porous 2 200 kilometer border, which is perforated by well-worn drug trafficking and contraband routes.