National security adviser Jake Sullivan said the U.S. is still having "intensive discussions" with "Israel, Qatar and Egypt about how to best get traction on a strategy that will get all the hostages out."

“The President and I, along with Secretary [of State Antony] Blinken and [CIA] Director [William] Burns, will stay in touch with our Israeli and Qatari counterparts, as well as our Egyptian counterparts, to press Hamas on this issue," Sullivan said. "Right now, Hamas is refusing to release civilian women who should have been part of the agreement. And it is that refusal by Hamas that has caused the end of the hostage agreement, and therefore, the end of the pause in hostilities."

Over 100 people remain hostage in Gaza. National Security Council spokesman John Kirby said Sunday the U.S. thinks "about eight" Americans remain hostage.

"Of course, for the United States, the paramount priority is getting the American hostages out and we are talking to the president about all of his options in terms of securing the release of American hostages," Sullivan said. "Beyond that, I'm not going to comment because we need to be able to have those sensitive, diplomatic discussions behind closed doors."

-ABC News' Molly Nagle

In a heated exchange with a reporter, State Department spokesman Matthew Miller said that while it's proven Hamas deliberately targeted civilians to kill, he said he has not seen evidence that Israel is deliberately killing civilians.

"I'm surprised I don't hear more people saying, 'Why doesn't Hamas lay down its arms? Why doesn't Hamas move out of schools?'" Miller said.

At a different point in the briefing, Miller said Secretary of State Antony Blinken told Israeli officials during his recent trip to Israel that the U.S. would like to see more precision and restraint in Israel's operations in southern Gaza, compared to the initial bombardment in northern Gaza, to limit civilian casualties.

"We've seen a much more targeted request for evacuations here, where the Israeli Defense Forces have identified specific neighborhoods where they plan to conduct military operations, and urged in advance of those operations that people in those neighborhoods to move, rather than telling an entire city or an entire region to vacate their homes. So that is an improvement on what's happened before," he said.

Miller added, "They have instructed them to move to areas that we know are deconfliction zones. It's one of the things we discussed with them last week."

-ABC News' Matt Seyler

The women and children freed from captivity in Gaza all lost between 10% to 15% of their body weight, according to Dr. Yael Moze from the Schneider Children's Medical Department.

One family took three showers during their 54 days held hostage, while one child hostage took no shower during all 54 days in captivity, Moze said.

Hostages also suffered psychological abuse, Moze said, recalling one teenager who was allegedly told he'd be held hostage for at least a year.

As Israel steps up its bombing campaign again, all telecommunications have been knocked out in the Gaza Strip, according to the Palestine Telecommunications Company, or Paltel.

"We regret to announce that all telecom services in Gaza Strip have been lost due to the cut off of main fiber routes. Gaza is blacked out again," Paltel said.

Six Palestinian mothers of premature babies evacuated from the Gaza Strip last month were due to leave the war-torn territory on Monday for Egypt, where their young children remain hospitalized, Palestinian authorities said.

The Palestinian border authority published a list of mothers approved to leave Gaza on Monday via the Egptian-controlled Rafah border crossing and asked them to head there.

Last month, 28 babies born prematurely in Gaza City's besieged Al-Shifa Hospital were transported to Egypt after their incubators shut down amid a collapse of medical services during Israel’s bombardment. Five of the mothers traveled with their children to Egypt, but Egyptian officials said at the time that the status and whereabouts of the other parents were not known.

-ABC News' Ayat Al-Tawy and Morgan Winsor