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.

The United States believes eight Americans are still being held hostage by militants in the war-torn Gaza Strip, according to White House National Security Council spokesperson John Kirby.

"We think there's about eight hostages that are Americans. We know of at least one woman in that group," Kirby told ABC News' George Stephanopoulos in an interview Wednesday on "Good Morning America."

"We're doing everything we can to try to get them released," he continued. "We're constantly engaged with our partners in the region to try to get this humanitarian pause back in place, so that the flow of hostages can renew."

Although a temporary cease-fire between Israel and Gaza's militant rulers, Hamas, ended last week, the U.S. is "still flowing in humanitarian assistance" to civilians in Gaza, according to Kirby.

"And we're trying to get it up to the level that it was during the pause," he noted.

When asked about what Israel's "endgame" might be in its war against Hamas as Israeli troops expand their offensive across all of Gaza, Kirby said: "That's really something for the Israeli's to speak to."

"We obviously want to see Hamas eliminated as a threat to the Israeli people," he added. "That hasn't been achieved yet. They're going after the leadership as best they can. They believe they need to operate in the south. We've told them you know we’ll continue to support their military operations but we want to make sure that as they do that they're factoring in those innocent civilian lives as much as possible."

-ABC News' Morgan Winsor