(NewsNation) — The United Nations blames lack of supplies and insecurity for its decision to suspend food distribution to the Gaza city of Rafah via a newly built pier constructed by the U.S. military.

“It’s a chaotic situation because we’re trying to deliver aid in the middle of war zone,” Stéphane Dujarric, spokesperson for the United Nations secretary-general, told NewsNation’s “Elizabeth Vargas Reports.”

“It’s heartbreaking. What other reaction can you have as a human being?”

The U.N. suspended food distribution in the southern Gaza city of Rafah on Tuesday due to a lack of supplies and the danger associated with Israel’s expanding military operation. The U.N. warned that humanitarian operations across the territory were nearing collapse.

But Wednesday the U.N. World Food Program said it has handed out in Gaza in recent days a “limited number” of high-energy biscuits that arrived from a U.S.-built pier,

“Aid is flowing” from the pier, Jake Sullivan, U.S. national security adviser, told reporters Wednesday in response to questions about the troubled launch of aid deliveries from the maritime project. “It is not flowing at a rate that any of us are happy with.”

Hundreds of thousands of Palestinian civilians have fled Rafah in recent weeks, anticipating a full-scale offensive by Israel’s military. But many thousands remain.

Since the U.S. finished building a temporary pier to bring in aid by sea, many of the trucks have been overrun and their contents taken.

“People are starving, and they see an aid truck,” Dujarric said. “They haven’t seen one in weeks. They don’t know when the next one will come. It’s almost a type of self-distribution.”

The aid trucks are not defended by soldiers, Dujarric said.

“We’re humanitarians. We don’t work with the military. The security has to come from the community. And the security comes from the community when they know the aid will be consistent — when they know there will be regular distribution of aid.”

And that, he said, can’t happen if the U.S. pier is the only route for aid to enter Gaza.

“The only way to have sustained humanitarian access is by land routes. We need to (have) all the crossings open, and open consistently.”

The U.N.’s World Food Program said it was running out of food for central Gaza, where hundreds of thousands of people are now living.

“Humanitarian operations in Gaza are near collapse,” said Abeer Etefa, a WFP spokesperson. If food and other supplies don’t resume entering Gaza “in massive quantities, famine-like conditions will spread,” she said.

The Associated Press contributed to this report