Venezuelan doctors have called on the military to unblock the Tienditas International Bridge so humanitarian aid can reenter the country.
They protested on the Colombian side of the border to avoid repercussions at a time of huge political tension.
Opposition leader Juan Guaidó has proclaimed himself interim president after claiming Nicholas Maduro's presidency is illegitimate.
The US has imposed harsh sanctions on the country's oil exports.
Jens Laerke, a spokesman for the UN Office for the Coordination of Humanitarian Affairs, is committed to delivering aid.

At least 9 killed in hotel fire in India's Kolkata
Ebola cases in Congo exceed 5,000, government data shows
8 Israeli airstrikes hit Syria's Abu al-Duhur airbase, state TV reports
Indonesia earthquake death toll rises to 70, government aid arrives
China's torrential rains kill 10 in southwest as thousands evacuated
