The moves come amid preparations for an opposition rally on Tuesday -- Youth Day -- that National Assembly head Juan Guaido said is intended to "send a message" to the military, which has so far stood by leftist President Nicolas Maduro.
Humanitarian aid has emerged as a central challenge to Maduro since Guaido declared him illegitimate and proclaimed himself interim president last month.
The military has refused to allow passage into the country of food and medicine stockpiled in Cucuta, Colombia on Venezuela's western border, with Maduro calling it a "political show" and a pretext for US intervention.
Guaido's envoys, meanwhile, met with Brazilian officials in Brasilia and announced plans to establish a second aid storage center in the state of Roraima, on Venezuela's southeastern border.
Guaido's ambassador to Brazil, Maria Teresa Belandria, said she had received assurances from Brazilian Foreign Minister Ernesto Araujo over the new aid center.
"In coming days we will visit the state of Roraima to see where this storage center will be and from next week we will organize the arrival of this humanitarian aid," Lester Toledo, head of Guaido's aid distribution team, told reporters.
The test of wills over aid comes amid a severe economic crisis in Venezuela, where life-threatening shortages of food and medicine and intensifying hyperinflation have driven more 2.3 million people to flee the country.
Guaido, who has been recognized by some 50 countries as interim president, has pointedly warned the military that blocking aid was a "crime against humanity."
According to the opposition leader, 300,000 people risk death if the supplies are not brought in soon.
"We're mobilizing all over the country to ensure the humanitarian aid enters so we can deal with this crisis," said Guaido.
He said almost 100,000 Venezuelans have signed up as volunteers to help bring in the aid and distribute it to those most in need.
On Sunday, dozens of doctors protested on the Venezuelan side of the border demanding the aid, which started arriving at the Colombian town of Cucuta on Thursday, be allowed in.
But the armed forces have blockaded the border bridge linking the two countries.
'Crime against humanity'
"This a crime against humanity, men of the armed forces," said Guaido on Sunday.
He has offered amnesty for any members of the armed forces who disavow Maduro.
The National Assembly President wants to oust Maduro and set up a transitional government ahead of new elections.
On Sunday, the Venezuelan military announced it had started conducting exercises, set to run until February 15, to "reinforce the country's defensive capacity."
Tuesday's march, in part to remember the estimated 40 people killed in clashes between protesters and the security services since January 21, aims to increase the pressure on Maduro to step aside.
Guaido warned that the military would be held responsible for the deaths of protesters.
The US is using sanctions as an attempt to starve Maduro's regime of its funding.
More than 40 percent of Venezuela's oil, which makes up 96 percent of its revenue, is sold to the US.
Pope Francis has said he would be prepared to mediate between the rival leaders but Guaido has rejected negotiations with Maduro, believing he would use them to buy time.
While keen on papal mediation, Maduro was less impressed last week when a group of European and Latin American ministers called for new presidential elections. Maduro accused them of bias.
Last week he also rejected a call by European Union countries to hold elections, prompting them to recognize Guaido.