An aid convoy is expected to leave for Madaya, a Syrian town under government siege, where people are reported to have been starving to death.
A convoy which had been due to reach the rebel-held town on Sunday was delayed by last-minute hitches.
Some 40,000 people are in Madaya, near Lebanon's border, with residents said to be eating pets and grass to survive.
The World Food Programme (WFP) earlier had hoped to take a first shipment of food and medicine to Madaya.
Blockades have been a feature of Syria's civil war but the plight of Madaya has drawn international attention, partly due to images emerging of severely malnourished residents.
Up to 4.5 million people in Syria live in hard-to-reach areas, including nearly 400,000 people in 15 besieged locations who do not have access to life-saving aid.
Madaya has been besieged since early July by government forces and their allies in Lebanon's Shia Islamist Hezbollah movement.