Israeli Prime Minister Benjamin Netanyahu said Wednesday evening that "there will be no cease-fire without the release of our hostages -- everything else is false."

National Security Council spokesman John Kirby said there are about 500 to 600 Americans and family members remaining in Gaza.

Asked if the lack of humanitarian pauses is a factor in why hundreds of Americans remain in Gaza, Kirby said it’s among the many "complicating factors."

Kirby would not confirm Axios' report that President Joe Biden is asking Israeli Prime Minister Benjamin Netanyahu for a three-day pause to allow progress in releasing more hostages, but Kirby said that discussions are ongoing with Israel, noting that there have been pauses in the past.

Kirby said they are trying to get an agreement "for as many pauses as might be necessary to get all of them out," but called it a "delicate negotiating process," and laid out some of the options that are being floated.

"What we're talking about here is temporary, fixed in time, short duration, hours to days, depends on the need. And then also localized in terms of the map," he explained. "So it would be an agreement that for a set period of time [in a set area] there will be a pause in the fighting. That doesn't mean that there won't be or couldn't be fighting outside that zone during that same period of time. So all of that has to get factored in and I have no doubt that on the Israeli side, as they look at each proposal, they'll think about the impact, potential impact, on their military operations on the ground or in the air."

-ABC News' Justin Ryan Gomez

Over one month since Hamas took more than 200 people hostage in Israel, National Security Council spokesman John Kirby said the administration is still "not aware of any specific proof of life."

"We don't have any indication to the contrary, that they aren't still alive. And so, we're certainly operating under that assumption," he said.

"We don't have a perfect picture about where everybody is, what condition they're in, or how they're being held," Kirby continued. "We cannot rule out the possibility that other groups than Hamas may have hostages that they're holding."

-ABC News' Justin Ryan Gomez

United Nations High Commissioner for Human Rights Volker Turk said both Hamas and Israel have committed war crimes since Oct. 7.

"The atrocities perpetrated by Palestinian armed groups on 7 October were heinous, they were war crimes -- as is the continued holding of hostages," Turk said.

"The collective punishment by Israel of Palestinian civilians is also a war crime, as is unlawful forcible evacuation of civilians," he added.

Dr. Ahmed Mokhallalati, the chief plastic surgeon at Al Shifa hospital in Gaza, told ABC News that he is unwilling to leave his scores of burn patients and stayed behind with the some 2,000 people left in the hospital complex and about 500 patients.

Mokhallalati said the hospital is virtually cut off because no one can get in -- they only received two or three patients on Saturday.

But despite having hundreds of burn patients, Mokhallalati doesn’t have much to do because they have only enough power for a single outlet to work. They use it in a clinic which has become the only operating room, because the real ORs require more power.

Mokhallalati said only about 15-20% of the hospital staff remain.

He also said there are some 40 infants in the neonatal units and 60 or so patients on ventilators, who he and the hospital administrators say will die once the generator fuel runs out.

The Israeli military’s civil coordinator said in a video statement Saturday that the eastern exit to the hospital is open, and that people are free to leave. But the images the Israeli military released from inside Gaza show that much of Gaza City and it’s outlying neighborhoods are flattened.

-ABC News' Matt Gutman and Sohel Uddin