More than 100 workers with UNRWA, the United Nations agency for Palestinian refugees, have been killed since Oct. 7, the highest number ever seen in a single conflict, the agency said.

Those killed include parents, teachers, nurses and doctors, said Philippe Lazzarini, commissioner-general of UNRWA.

"Devastated. … UNRWA is mourning, Palestinians mourning, Israelis mourning," Lazzarini wrote, again calling for a humanitarian cease-fire.

During brief remarks in New Delhi Friday morning, U.S. Secretary of State Antony Blinken swiftly acknowledged the Biden administration’s “appreciation” of Israel’s commitment to four-hour pauses with three-hour notice in specific areas and corridors of Gaza “that will allow people to move more safely, freely to get out of harm's way and also to access assistance.”

“At the same time, much more needs to be done to protect civilians and to make sure that humanitarian assistance reaches them," he continued. "Far too many Palestinians have been killed. Far too many have suffered these past weeks, and we want to do everything possible to prevent harm to them, and to maximize the assistance that gets to them.”

The secretary said they have established basic principles to guide the effort for lasting peace and security in the region: no use of Gaza as a platform for launching attacks against Israel, no diminution in the territory of Gaza and a commitment to Palestinian-led governance.

Blinken reaffirmed that the administration had “long been committed” to a two-state solution, and the terror attacks of Oct. 7, he said, only redouble American commitment to the peace process.

“But now we've had the events of October 7 -- the almost, beyond the human imagination -- horror of October 7. And I think that only reinforces us in our conviction and our commitment to durable and lasting peace which again, we see through two states,” he said.

On humanitarian assistance, Blinken said that “more than plans, we have a concrete way forward,” including ensuring that there are adequate supplies of fuel for the trucks coming in and that hospitals and desalination plants “have what they need.”

“It's always a process and moving from an understanding, moving from an agreement to implementation is what we're working on right now,” he said.

Any plans for short-term pauses in the fighting in Gaza must be carried out in coordination with the United Nations, said Stéphane Dujarric, spokesperson for the U.N. secretary-general.

The U.N.'s comments come after the White House said Israel agreed to daily four-hour pauses in northern Gaza to allow civilians to escape.

"How any such halt in the fighting, and how it would work for humanitarian purposes, will need to be coordinated with the United Nations, especially on the issue of timings and location," Dujarric said. "And obviously in order for this to be done safely for humanitarian purposes, it would have to be agreed with all parties to the conflict to be truly effective."

Another 65 aid trucks entered Gaza through the Rafah border crossing on Thursday, a border crossing official said.

A total of 821 aid trucks have now crossed into Gaza as the humanitarian crisis worsens.

The Israeli military on Monday accused Hamas militants of building "a whole tunnel system under" Sheikh Hamad Hospital in Gaza.

The practice of using hospitals as civilian shields has been "absolutely normal" for the militants, IDF spokesperson Jonathan Conricus said.

"Why it is this important? Because hospitals and other humanitarian facilities are supposed to enjoy special protections," Conricus said in a morning briefing. "But what Hamas is doing is that they've violating that special protection and using it for combat purposes."

More than 500 people have died in at least 102 strikes near or on health care facilities since Oct. 7, the World Health Organization said on Sunday.

"Over half of health attacks and over a half of hospitals damaged were in Gaza City," WHO officials said on social media. "Health care is #NotATarget."

During Monday's briefing, Conricus shared an IDF video that he said demonstrated there were Hamas tunnels under the hospital. He also shared several photos that he said dated back to at least 2010, when the hospital was being constructed. The groundwork for the Hamas tunnels was put in place at that time, he said. ABC News was not immediately able to verify the claims.

In a photo said to be from 2023, rocket-launching sites could be seen along the outskirts of the facility, Conricus said. He presented another photo of what he said was the opening of a Hamas tunnel on the grounds.

"We know that underneath this entire complex, there's an entire Hamas infrastructure underground," Conricus said. "And it is absolutely normal. This is how Hamas operates all around the Gaza Strip."

-ABC News' Kevin Shalvey