Israel-Gaza updates: Biden speaks with Netanyahu about hostages' release, Gaza humanitarian assistance

The United Nations Relief and Works Agency, which has been assisting people trapped in Gaza, said Sunday that it is on the verge of running out of fuel "critical" to keeping its humanitarian response going.

“In three days, UNRWA will run out of fuel, critical for our humanitarian response across the Gaza Strip," UNRWA chief Philippe Lazzarini said in a statement. “Without fuel, there will be no water, no functioning hospitals and bakeries. Without fuel, aid will not reach those in desperate need. Without fuel, there will be no humanitarian assistance."

The UNRWA, the largest humanitarian agency in the Gaza Strip, said it is sheltering about 500,000 people in Gaza out of the nearly 1 million people who have been displaced by the Israel-Hamas conflict, the agency said.

“I call on all parties and those with influence over them to immediately allow fuel supplies into the Gaza Strip and to ensure that fuel is strictly used to prevent a collapse of the humanitarian response," Lazzarini said.

Another small convoy of humanitarian aid trucks crossed into Gaza from Egypt Sunday, as the executive director of the U.N. World Food Programme told ABC News' "This Week" that the situation in the Palestinian territory has grown "catastrophic."

Live images from the Rafah crossing Sunday showed the trucks moving into Gaza. U.N. World Food Program Executive Director Cindy McCain said 17 aid trucks rolled across the border Sunday.

It remains unclear exactly what type of aid crossed the border, but the word "petroleum" was written on the sides of five of the trucks.

"The situation is catastrophic in Gaza right now," McCain said on "This Week." "There has been no food, no water, no electricity. You've heard all the stories. Yesterday, we were able to get 20 trucks to cross. And by that 20 trucks total, three of which were WFP."

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Current aid to Gaza is ‘not enough’: Cindy McCainABC News’ Jon Karl interviews Executive Director of the World Food Programme Cindy McCain on “This Week.”

ABCNews.com

McCain said the first shipment enabled the WFP to feed about 200,000 people during dinner Saturday.

"But that's not enough. That's a drop. We need -- we need secure and sustainable access in there, in that region, so that we can feed. This is a catastrophe happening and we just simply have to get these trucks in."

-ABC News' Ayat Al-Tawy

Israel Defense Forces spokesman Rear Adm. Daniel Hagari said Sunday that the military has notified the families of 212 hostages that their loved ones are being held by the Hamas militant group in the neighboring Gaza Strip.

That number has continued to increase as the IDF investigates the situation and gathers more information on Hamas' Oct. 7 attack on Israel.

The whereabouts of another 100 people remain unknown, according to Hagari.

-ABC News' Bruno Nota and Morgan Winsor

The volume of goods that entered Gaza after the Rafah border crossing opened on Saturday equated to "about 4%" of what is needed, according to the United Nations on Sunday.

U.N. officials said that at least "100 trucks per day" are needed to bring an adequate amount of aid into Gaza.

The United Nations Office for the Coordination of Humanitarian Affairs (OCHA) estimated about 1.4 million people in Gaza are displaced with over 560,000 people staying in "emergency shelters in increasingly dire conditions," according to a press release.