US military planes have been delivering humanitarian aid for Venezuela in the Colombian border town of Cucuta.
The aid is being stockpiled at the request of the Venezuelan opposition leader, Juan Guaidó, who declared himself interim president last month.
President Nicolás Maduro has alleged that the aid is part of a US plot to disguise an invasion into Venezuela.
Mr Guaidó said some 600,000 Venezuelan volunteers would carry the aid across the border on 23 February.
“We will mobilise within and outside our borders,” he said in a tweet on Saturday, adding: “Our struggle continues to yield results!”
It remains unclear if the aid will be allowed to enter Venezuela.
Speaking at a news conference in Cucuta, USAID administrator Mark Green said the aid had been requested by Mr Guaidó because
Venezuela was in the grip of a growing humanitarian crisis.
“Children are going hungry, and nearly every hospital in Venezuela is experiencing serious medicine shortages.”
He said the crisis had reached regional proportions, with three million Venezuelans migrating to neighbouring countries in search of food and medicine.
Mr Guaidó, who has been recognised by the US and most Western governments as interim president of Venezuela, said hundreds of thousands of volunteers had signed up to create brigades to help get the aid into the country.
