Venezuelan military officers blocked a bridge on the border with Colombia ahead of an anticipated humanitarian aid shipment Tuesday, as opposition leader Juan Guaido stepped up his challenge to President Nicolas Maduro's authority.
The opposition-dominated National Assembly had earlier warned the armed forces, which make up much of Maduro's power base, not to cross a "red line" by blocking aid.
"You know there's a red line, you know well there's a limit, you know that medicines, food and medical supplies are that limit," lawmaker Miguel Pizarro said in a message to the military.
The aid delivery was being coordinated by Guaido, who has declared himself interim president of the oil-rich country and now enjoys the backing of some 40 countries as Venezuela's legitimate leader.
Franklyn Duarte, an opposition lawmaker from the border state of Tachira, told AFP that troops from the armed forces were blocking the crossing.
Guaido, 35, claims his legitimacy from the constitution and has been ramping up pressure on Maduro by calling his supporters out into the streets.
The next mass demonstration is due for February 12.