Israel-Gaza updates: Israel says ground operation underway in southern Gaza

With the temporary Israel-Hamas cease-fire now over, National Security Council spokesman John Kirby told ABC News' "This Week" that the U.S. is "working at this literally by the hour … if we can get these discussions back going" to get a new pause in place.

Kirby said the Israel-Hamas agreement "fell apart because Hamas was unwilling and refused to come with additional [hostage] lists of women and children -- which we know they are holding -- and put them on the list so that Israel can evaluate that and we can get them exchanged."

Kirby said the U.S. thinks "about eight" Americans remain hostage.

He added, "We don’t have perfect visibility on where they all are, we certainly don’t have perfect visibility on their physical or mental condition."

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Israel ‘receptive’ to US messaging on minimizing civilian casualties: John Kirby

George Stephanopoulos interviews National Security Council coordinator John Kirby on “This Week.”

ABCNews.com

When asked Sunday about The New York Times report alleging Israel knew about Hamas' attack plan a year in advance, Kirby said the U.S. had no knowledge of the Hamas planning document.

He added, "The focus has got to be on making sure Israel has what it needs to go after Hamas leadership."

The United Nations said 138,000 liters of fuel entered Gaza on Saturday -- the highest amount in one day since the Israel-Hamas war began.

Trucks with food, water, medicine and medical supplies also entered Gaza on Saturday, according to the U.N. Office for the Coordination of Humanitarian Affairs.

Hundreds of demonstrators gathered on Saturday at the first anti-government protest held in Tel Aviv since Oct. 7.

"We don't want a radical government. We didn't want it before, and we don't want it now," Moshe Radman, who helped organize the protest, told ABC News. "We are telling them we want a new government as soon as possible."

Radman says people were scared to protest in the early days of the war -- but that things have changed in the last few weeks. He predicts the demonstrations will grow.

"We gave them 57 days, and week after week we saw that they are not doing the right thing. And I think we understand that we are headed towards a long war, so we have to do it now," he said.

Protesters Sharon and Eyal Eshel said their 19-year-old daughter Roni, an Israel Defense Forces soldier, was killed in the Oct. 7 attack by Hamas militants while stationed at the Nahal Oz kibbutz. Her family said they have yet to receive a single phone call from Israeli Prime Minister Benjamin Netanyahu.

"We are looking for answers, we want answers from the IDF, we want answers from the government. And we want the man who is in charge, we need him to take responsibility," Sharon Eshel told ABC News.

"It's not the time to say, 'It's not the time,'" Eyal Eshel told ABC News, calling on Netanyahu to sit down with him and answer his questions. "Enough is enough."

In response to criticism and pool polling numbers, Netanyahu has previously said he has no plans of stepping down.

-ABC News' Dragana Jovanovic, Dorit Long, Kuba Kaminski and Ines De La Cuetara

Secretary of Defense Lloyd Austin called on Congress to pass aid to Israel and Ukraine during a keynote speech Saturday at the Reagan National Defense Forum in California.

He said support for Israel's security is "non-negotiable."

"We still urgently need bipartisan support in Congress to pass the supplemental to rush security assistance to our partners in Ukraine, in Israel and elsewhere," he said.

Austin said peace is "not self-executing" and that America should remain involved and in leadership.

"From Russia to China, from Hamas to Iran, our rivals and foes want to divide and weaken the United States -- and to split us off from our allies and partners," he said. "So at this hinge in history, America must not waver."

-ABC News' Kelly Livingston