Madaya, Syria (BBN)-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.
"We are pretty confident," UN refugee agency spokesperson Melissa Fleming told the BBC.
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.
"I have just got confirmation that our humanitarian convoy will leave tomorrow (Monday) morning," Fleming said.
"This is typical that it takes a while - the administrative hurdles are constant," she added.
Meanwhile, Brice de la Vigne from the Medecins Sans Frontieres (MSF) medical charity described the situation in the town as "quite horrific".
de la Vigne, whose organisation has been in contact with doctors inside Madaya, told the BBC that more than 250 people there had "acute malnutrition".
He added that "10 of them need immediate medical evacuation" or they would die.
The World Food Programme (WFP) earlier had hoped to take a first shipment of food and medicine to Madaya.
It was not clear what caused the delay but the BBC's Jim Muir in Beirut says negotiating access across battlefronts in a siege situation has always been a tricky business.
It involves agreement at the top political level on both sides of the conflict, as well as individual fighters on the ground.
A similar operation for two government-held villages in the north - Kefraya and Foah - has also been discussed.
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.
The situation in Foah and Kefraya, under siege from rebels, is also reported to be worsening, with an estimated 30,000 people trapped.
WHAT'S HAPPENING IN SYRIA?
More than 250,000 Syrians have lost their lives in almost five years of conflict, which began with anti-government protests before escalating into a brutal civil war.
More than 11 million others have been forced from their homes as forces loyal to President Bashar al-Assad and rebels opposed to his rule battle each other - as well as jihadist militants from Islamic State.
WHY ARE CIVILIANS UNDER SIEGE?
All parties to the conflict are using siege warfare, encircling populated areas, preventing civilians from leaving and blocking humanitarian access in an attempt to force opponents to surrender.
Shortages of food, water, medicine, electricity and fuel have led to malnutrition and deaths among vulnerable groups.
WHERE ARE THE SIEGES?
Government forces are besieging various locations in the eastern Ghouta area, outside Damascus, as well as the capital's western suburb of Darayya and the nearby mountain towns of Zabadani and Madaya.
Rebel forces have encircled the villages of Foah and Kefraya in the northern province of Idlib, while IS militants are besieging government-held areas in the eastern city of Deir al-Zour.
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