The United Nations' World Food Programme said Tuesday it is unable to help 1 million Syrians who are going hungry.
This month, the agency aims to help 1.5 million of the 2.5 million Syrians that the Syrian Arab Red Crescent says need it, spokeswoman Elisabeth Byrs said.
The lack of security and the agency's inability to use the Syrian port of Tartous for its shipment means that a large number of people in the some of the country's hardest hit areas will not get help, she said.
"Our main partner, the Red Cross, is overstretched and has no more capacity to expand further," Byrs said.
She also said that the agency has temporarily pulled its staff out of its offices in the Syrian cities of Homs, Aleppo, Tartous and Qamisly due to the rising dangers in those areas.
But in December, WFP was able to reach for the first time in many months some hard-to-reach areas near the Turkish border, she said.
Riot breaks out at refugee camp in Jordan
Meanwhile, a riot broke out at a Jordanian camp for Syrian refugees on Tuesday, with aid workers attacked with sticks and stones.
Refugees were frustrated after cold, howling winds swept away their tents and torrential rains flooded muddy streets over night.
Police said seven aid workers were injured.
Ghazi Sarhan, spokesman for The Jordan Hashemite Charitable Organization, said frustration over the harsh conditions triggered the riot. The charity runs the camp along with the UN refugee agency, UNHCR.
Dozens of refugees hit the workers with sticks and pelted them with stones as they distributed bread for breakfast.
The riot broke out after the region's first major winter storm this year hit the Zaatari refugee camp, home to nearly 50,000 refugees in Jordan's northern desert. Inside the camp, pools and lakes surrounded tents, stranding refugees including pregnant women and infants.
Rain was intermittent and the wind had subsided by Tuesday. But there were warnings a large snowstorm could hit Turkey and Jordan on Wednesday. Temperatures dipped below freezing overnight and were expected to be similar late Tuesday night into Wednesday.
'It is hell'
"It is hell — boiling hot in the summer and freezing cold now," lamented Ahmed Zibi, 45, who said he spent the night watching over his five children when his tent collapsed. "Rain flooded the tent and its shafts submerged and collapsed on us."
The refugees may be about to face even deeper misery with warnings of a major snowstorm threatening Jordan and Turkey — the two countries with the largest Syrian refugee populations.
'It's one misery after the other as the international community sits idle.' —Fadi Suleiman, Syrian refugee in Jordan
Fadi Suleiman, 30, said camp conditions were "worse than living in Syria," where rebels are fighting a civil war against authoritarian ruler Bashar al-Assad that has killed some 60,000 in nearly two years of fighting.
"It's one misery after the other as the international community sits idle, doing nothing to help us get rid of the tyrant Assad," he said. "But this one is dangerous: There's a serious storm that could kill children and old people."
Of Zaatari's nearly 50,000 refugees, at least half are under the age of 18. They are part of more than 280,000 who fled to Jordan since the revolution against Assad broke out in March 2011.
The Syria crisis began with peaceful protests in March 2011 but has since shifted into a civil war. At least 60,000 people have been killed in the conflict, according to a recent UN estimate.