ISTANBUL -- With the fourth wartime winter for Syrians just around the corner, the United Nations is warning that its humanitarian effort is dangerously low on funding.

Millions of Syrians could go hungry or have to endure the winter months without proper shelter, medical attention and fuel if the U.N. doesn't receive more funding soon, according to U.N. agencies working within Syria and cash-strapped neighboring countries.

In its biggest humanitarian appeal to date, the U.N. this year has requested $3.74 billion for the surrounding region, to fund humanitarian operations related to the war. The U.N. said it has received only 52 percent of that annual figure. Of the additional $2.28 billion the U.N. says it needs for humanitarian operations within Syria, it has received only 39 percent.

Humanitarian support to Syrians this winter will cost the U.N. $113 million, according to estimates. This aid includes funding for shelters, hospitals, clinics, winter clothing, blankets and other forms of support to help Syrians survive the harsh weather conditions.

The U.N.'s World Food Program, which feeds Syrians in Syria, Lebanon, Jordan, Iraq, Turkey and Egypt, says it will be forced to slash some of its food voucher programs in November and December if more funding doesn't come through. Food parcels inside Syria were already cut in size by 40 percent in October due to a funding shortfall.

WFP's spokesperson in Amman, Joelle Eid, says the organization wasn't so pressed for cash last year. But now major cuts may have to be made as funding dries up.

"This will have horrendous effects on the lives of these families who consider it a lifeline," she told WorldPost. "Children will be forced to drop out of school and work. We would see an increase in child marriage, and many families would go back to Syria even if their area is unsafe."

It costs WFP a staggering $35 million a week to feed 6 million at-risk Syrians.

Time is running out, Yacoub El Hillo, the U.N. Resident and Humanitarian Coordinator in Damascus, told WorldPost over Skype from Damascus.

"I am worried that the suffering of the Syrian people is now eclipsed by the attention given to ISIL," he said, referring to the extremist group in Syria and Iraq that calls itself the Islamic State, "but also by the military action, at the expense of the people who are the key victims."

"I fear this is coming at a moment when winter is fast setting in in the region," he said. "Even if they were able to cope in previous years, I think it's going to be more difficult this time."

While the U.N. Security Council passed a resolution this summer that authorized the distribution of humanitarian aid to Syrians without the regime's consent, the Syrian government and some opposition groups continue to block access to parts of Syria as the humanitarian situation deteriorates. Fuel prices are skyrocketing, and civilians are falling deeper into poverty, often living on a few dollars a day.

The U.N. Office for the Coordination of Humanitarian Affairs has compiled an up-to-date list detailing how much individual countries have pledged, and which countries have yet to follow through on their promises.

"The world can do better," El Hillo insisted. "Donors can be more generous. Not to do so condemns millions of people. It will be a problem not only for Syria but also for Syria's neighbors."

The U.N.'s Director of Humanitarian Operations John Ging has warned that the countries bordering Syria are at their "breaking point."

While roughly 6.5 million Syrians are displaced within the war-ravaged country, more than 3.2 million have fled across its borders, mostly pouring into Lebanon, Jordan and Turkey.

At a major humanitarian conference in Berlin on Oct. 29, Turkey's Deputy Foreign Minister Naci Koru blasted the international community for not taking a larger role in aiding Syria's neighbors, which have borne the brunt of the refugee crisis.

On the streets of Turkey's cosmopolitan Istanbul, destitute Syrian families wrapped in blankets beg for spare change. Along the border, many refugees who can't find a place in the already packed refugee camps sleep in bare-roomed apartments and cold bus stations.

Meanwhile, Jordan has warned it can no longer accept refugees as it has for three and a half years. And refugees are also being turned away from Lebanon, where Syrians now make up nearly a quarter of the population.