The UN warned on Thursday that it will be forced to cut food rations for more than 6 million Syrians from next month unless it received more funding.

The World Food Programme said that while it still expects to reach almost 6 million Syrians inside the country and in neighbouring states in October and November, there will be significant cuts to the amount of food delivered. The WFP said it had no money for programmes in December.

A WFP official told Reuters that the food basket for Syrians could shrink to 825 calories, well under half the daily recommended intake.

Cash payments and voucher schemes will be cut by up to half in Jordan, Egypt, Lebanon and Iraq. School feeding programmes for about 12,000 children in Iraq have already stopped.

“We have reached a critical point in our humanitarian response in Syria and in neighbouring countries and unless we manage to secure significant funding in the next few days, I am afraid we will have no choice but to scale back our operation,” said Muhannad Hadi, WFP’s regional emergency coordinator for the Syrian crisis.

John Ging, director of operations at the UN Office for the Coordination of Humanitarian Affairs, told Reuters: “In October, WFP will be able to deliver 60% of what they have been delivering. In November it will be down to 40%.

“It is because the money is not coming in. This is devastating news for people who are aid-dependent.

There is a three month lag between the time food supplies are purchased and delivered on the ground, Ging said. “This will come at a time when the suffering is exacerbated by winter.

“So we will find humanitarian agencies cutting down on aid deliveries when aid is needed more than ever,” he said. “It is not just food, it is vital shelter material, clothing and supplies for water and sanitation.”

Ging said the WFP needed $44m for its immediate operations in Syria. A further $56m is needed to avoid cuts in food assistance in neighbouring countries, diplomats said.

Yacoub El Hillo, UN resident coordinator in Damascus, told Reuters that the lack of funds had created a “really critical situation”.

“Syria is the most complex and most urgent and largest operation, but it is one of many. Donors are [only] able to do so much,” he said, noting competing pressures for funding, from the Ebola crisis in west Africa, South Sudan and the Central African Republic.

In July, the UN security council authorised the delivery of emergency aid across the Syrian border without the consent of Damascus. To date 14 UN convoys have entered Syria via Turkey and Jordan, Ging said.

“We have been gaining access for the first time to some besieged and hard to reach areas we have never been able to reach before. We have more access opportunities, but are not able to scale up because of funding. You can’t deliver what you don’t have.”