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.

Indonesian mosque blasts injure dozens, teenage suspect identified
Over 200 flights delayed at Delhi airport after glitch in air traffic system
India top court says Air India crash report does not insinuate anything against pilot
Belgium's Liege airport temporarily halted again due to drone sighting
Sudan's RSF agrees to US proposal for humanitarian ceasefire
