Top UN officials have warned that the withdrawal of funding for its main aid agency in Gaza could lead to the "collapse of the humanitarian system".
They spoke out after the US, UK and other countries halted funding over the alleged role of some UN staff in the 7 October Hamas attacks on Israel.
The UN sacked several of its staff over the allegations.
It said an investigation into its agency for Palestinian refugees, UNRWA, is underway.
Israeli Prime Minister Benjamin Netanyahu has described UNRWA as "perforated with Hamas", saying Israel has "discovered that there were 13 UNRWA workers who actually participated, either directly or indirectly, in the 7 October massacre".
But the US, the biggest donor to the UNWRA, has said it wants to see the aid agency continue its work.
"There is no other humanitarian player in Gaza who can provide food and water and medicine at the scale that UNRWA does," US State Department Spokesman Matthew Miller said.
"We want to see that work continued which is why it is so important that the United Nations take this matter seriously, that they investigate, that there is accountability for anyone who is found to have engaged in wrongdoing."
In the attack on 7 October, Hamas gunmen killed about 1,300 people and took about 250 hostages.
Israel launched an offensive against Hamas in response and more than 26,700 people have been killed in Gaza since then, according to the territory's Hamas-run health ministry.
More than half of Gaza's buildings have been damaged or destroyed during the offensive, new analysis seen by the OceanNewsUK has revealed.
UN Secretary General António Guterres has said a full independent investigation into UNRWA is under way,
A UNRWA spokesperson has said that if funding is not resumed, the agency will not be able to continue its operations beyond the end of February.
"The allegations of involvement of several UNRWA staff in the heinous attacks on Israel on 7 October are horrifying," a statement by the UN Inter-Agency Standing Committee says.
"As the secretary-general has said, any UN employee involved in acts of terror will be held accountable. However, we must not prevent an entire organisation from delivering on its mandate to serve people in desperate need.
"Withdrawing funds from UNRWA is perilous and would result in the collapse of the humanitarian system in Gaza, with far-reaching humanitarian and human rights consequences in the occupied Palestinian territory and across the region," it adds. "The world cannot abandon the people of Gaza."
Also on Tuesday, the UN's humanitarian coordinator for Gaza said no other organisation can replace UNRWA due to the the agency's "knowledge" of the population in Gaza.
Other countries which have halted funding include Germany, Sweden an Japan.
Mr Guterres met representatives of more than 30 donor states on Tuesday and is reported to have urged those who have withdrawn funding to reconsider.
