Maduro has also rejected humanitarian aid being amassed by the United States, which has already been welcomed by Guaido, calling it a political "cheap show".
The United States is engaged in direct contacts with members of Venezuela's military encouraging them to pledge allegiance to opposition leader Juan Guaido and is working on new sanctions to ramp up pressure on the country's incumbent President Nicolas Maduro, Reuters reported, citing a senior White House official.
In the Colombian border town of Cucuta, where the first US aid arrived Thursday, the American ambassador called on the Venezuelan security forces to allow the aid in.
Guaido declared himself Venezuela's interim president January 23, maintaining that the constitution gives him that right as head of the opposition-controlled National Assembly because Maduro's re-election should be considered legitimate. Inflation has skyrocketed, and since 2015, more than three million Venezuelans have fled to neighbouring countries due to scarcity of food, jobs and medicine.
"We will succeed in letting the humanitarian aid in, because it's about saving lives", Guaido posted on his official Twitter feed.
Guaido says the May 2018 vote in which Maduro won a second term as president was a sham and on January 23 invoked a constitutional provision to declare himself president, promising free and fair elections.
In a plea for the aid to pass through, exiled politician and Guaido's spokesperson in Colombia, Lester Toledo, sent a message to Venezuela's military. Dozens of political parties that make up Venezuela's opposition have failed to mount a viable political challenge.More news: Did Rob Gronkowski sort of hint he's playing in 2019?
Last month, the 35-year-old Guaido was named leader of the opposition-controlled National Assembly.
On Monday, Canada hosted a meeting of the Lima Group regional bloc to discuss how the global community can further help the people of Venezuela, including through immediate humanitarian assistance.
However, Guaido has rejected any negotiations, seeing it as a way for Maduro to buy time.
High protein energy supplements were also included for young Venezuelan children suffering from malnutrition.
"It's a awful scenario because it does not solve the problem and makes the situation in the country worse", said Leon.
The boxes of emergency aid came from the U.S. Agency for International Development, and are marked with USAID labels.More news: Massive drug bust exposes cartel ties between Mexico and Australia
"The humanitarian aid has become a show to justify an invasion of the country", Maduro said. He's offered to try to resolve the political impasse in a dialogue with opposition leaders, which critics call a stalling tactic that has failed to lead to any changes.
Venezuela is already experiencing mass hunger, and is likely to experience even greater difficulty importing food thanks to stepped-up USA sanctions. Maduro's security forces used freight containers and a tanker trailer to block the global bridge near where the aid is arriving.
But as the gathering got underway, tensions were playing out farther north in the Colombian border town of Cucuta.
"The military sector needs face-to-face negotiations" with specific officials, "an worldwide guarantor and probably a pardon being enshrined in the constitution", he said.
Venezuela's army had to choose between "a dictatorship that does not have an iota of humanity, or to side with the constitution" from which he takes his legitimacy, Guaido said in an interview on Colombian radio.
Lester Toledo, who is representing opposition leader Juan Guaido in the aid mission, issued a message to troops, telling them the aid contains food and medicine their own families need.More news: COLLUSION COLLAPSE: President Trump Reacts to Senate Intel Chair's 'No Collusion' Comments