Sky News has seen multiple warehouses in the Jordanian capital Amman, packed full of critical aid earmarked for the Gaza Strip.
There are three other similar locations in the country and run by the Jordanian authorities holding aid intended for Gaza.
There are also large amounts of aid being stored separately by the United Nations in Jordan.
Both the Jordanian authorities and the UN say the majority of aid collected has been sitting in Jordan since March, with only a negligible amount of aid being allowed into Gaza because of Israeli restrictions on aid going into the Strip.
The news comes as tens of thousands of families living in tents in Gaza have been affected by flooding following heavy rains across the region.
The stored aid is equivalent to thousands of trucks' worth of aid - in Jordan alone.
And the United Nations says there's even more aid being held back in Egypt too - in total, enough aid to provide food for the entire Gaza population for about three months, according to the deputy commissioner general for UNRWA, Natalie Boucly, who was interviewed by The Guardian.
Sky's special correspondent Alex Crawford, who is in Amman, said: "The aid in Jordan alone includes critical supplies such as tents and tarpaulins as well as blankets, mattresses, medicines like paracetamol as well as baby formula ..... all being stored here and held back, according to the UN here in Jordan and the Jordanian authorities, all being refused entry by the Israelis."
What has UNICEF said?
The UN aid agency for children has called on Israel to allow all of its supplies into Gaza.
Writing on X, UNICEF said it had already distributed more than 5,000 tents, 220,000 tarps and 29,000 winter clothes kits.
The Israeli defence body in charge of humanitarian aid in Gaza, COGAT, has said it is allowing in winter materials including blankets and tarps, which are water-resistant sheets made of canvas or plastic used for protection from the elements.
But aid organisations have warned the efforts are completely inadequate and vastly outnumbered by those in need - an estimated 1.4 million people are classified as vulnerable by aid agencies.
In contrast, on X, COGAT said it had "facilitated close to 140,000 tarpaulins directly to the residents of the Gaza Strip" and had spent the past few months coordinating with the international community.
It went on: "We call on international organisations to coordinate more tents and tarpaulins and other winter humanitarian responses."
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But the United Nations insists Israel is in breach of international humanitarian law and has the responsibility as the occupying force to ensure the safe distribution and coordination of life-saving aid.
What does the Israeli military say?
An Israeli military official told Sky News that aid was stopped from Jordan after the main border crossing with Israel was closed following an attack there in September, which saw a Jordanian truck driver kill two Israeli soldiers.
They said the crossing will not be opened until an investigation is concluded into the incident. They pointed out that there are other routes for aid to enter Gaza along the Egypt border, and hundreds of trucks enter the strip every day under the Israel-Hamas ceasefire agreement.
Meanwhile, in the sprawling Muwasi tent camp in Gaza, winter's first strong rainfall sent water cascading through the flimsy tents, which are now homes to tens of thousands of displaced families.
Residents tried to dig trenches to keep the water from flooding their tents, as intermittent rains that began on Friday poured through tears in tarpaulins and makeshift shelters.
'Water puddles are inches high'
Assil Naggar said he "spent all (Friday) pushing water out of my tent", adding his neighbours' tents and belongings were wrecked.
"Water puddles are inches high, and there is no proper drainage," he continued.
The UN said Muwasi was sheltering up to 425,000 displaced Palestinians earlier this year, the vast majority in makeshift temporary tents, after Israel's war with Hamas displaced most of Gaza's population of more than two million people.
The bulk of Gaza's infrastructure is estimated to have been destroyed or badly damaged during the Israeli bombardment.
What's the latest with the ceasefire?
The first stage of the ceasefire agreement between Israel and Hamas, which took effect on 10 October, is now nearing its end with Israeli forces pulling back to a 'yellow line' and Hamas releasing all living Israeli captives who were held in Gaza.
Hamas has yet to return the remains of three more hostages, which Israel is demanding before progressing to the second stage, which includes an international stabilisation force to oversee security in Gaza.
On Monday, the UN Security Council is expected to vote on a US proposal for a UN mandate for such a force despite opposition from Russia, China and some Arab countries.
The Israeli bombardment of Gaza has gone on for more than two years, killing nearly 70,000 Palestinians, mostly women and children, according to the Hamas-run Gaza health ministry, which does not distinguish between civilians and combatants.
The Israeli military campaign came in response to attacks inside southern Israel by Hamas militants on October 7 2023, which saw 1,200 people killed and 251 taken hostage.
(c) Sky News 2025: Inside Jordan warehouse where Gaza aid held 'after being refused entry by Israel'
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