Palestinians jammed into their last refuge in Gaza voiced growing fear on Wednesday that Israel will soon launch a planned assault on the southern city of Rafah.
UN humanitarian chief Martin Griffiths warned of an impending "slaughter" in Gaza if Israel pushes ahead with its assault on the border city, where around 1.5 million Palestinians are seeking shelter.
"Today, I’m sounding the alarm once again: Military operations in Rafah could lead to a slaughter in Gaza. They could also leave an already fragile humanitarian operation at death’s door," the UN's Under-Secretary-General for Humanitarian Affairs and Emergency Relief Coordinator said in a statement.
"We lack the safety guarantees, the aid supplies and the staff capacity to keep this operation afloat."
The UN official's warning came as negotiations to pause Israel's war on Gaza and free the remaining hostages headed into a second day in Cairo.
The potential for further killings of civilians has triggered urgent appeals, even from close allies, for Israel to hold off sending troops into the last major population centre they have yet to enter in the four-month war.
Israel has killed over 28,000 Palestinians in its latest war on Gaza, including over 12,000 children, according to Gaza health authorities.
Recent weeks have also seen a flurry of diplomatic activity in Beirut, with foreign ministers including from Germany, France and Britain visiting in efforts to dial down Lebanon-Israel tensions.
Hezbollah fighters have traded near-daily fire with Israel since the war broke out on October 7.
Fears have been growing of another full-blown conflict between Israel and Hezbollah, with tens of thousands displaced and regional tensions soaring.
Late last month, Defence Minister Yoav Gallant said Israeli troops would "very soon go into action" near the country's northern border with Lebanon.