Stephanie Hallett, the chargé d'affaires of the U.S. Embassy in Jerusalem, posted a video on X showing her standing in front of the wreckage at Israel's Be'eri kibbutz, where many residents were killed by Hamas terrorists.

"It's really unbelievable," she said, choking up. "As a mother, and just as a human being, to see and to know what happened here, it's really important to say that we've been here, we've seen it, and it is evil. And we stand with Israel."

National Security Council spokesman John Kirby said the U.S. is working with its Israeli and Egyptian counterparts to secure safe passage out of Gaza for civilians.

"Civilians are not to blame for what Hamas has done," Kirby said. "I don't have an announcement to make today -- I can't tell you a specific route or corridor. I just want to make it clear that we are actively working on this with our Egyptian and our Israeli counterparts. Civilians are protected under the laws of armed conflict, and they should be given every opportunity to avoid the fighting."

-ABC News' Molly Nagle

Seventeen Americans are missing, including an unknown number of Americans being held hostage by Hamas, National Security Council spokesman John Kirby said.

"I think we all need to steel ourselves for the very distinct possibility that these numbers will keep increasing and that we may, in fact, find out that more Americans are part of the hostage pool," Kirby said.

He said the conditions and whereabouts of the hostages are not known.

"We don't know where they are, we don’t know if they're all in one group, or broken up into several groups. We don't know if they're being moved, and with what frequency and to what locations. All of those questions we're working hard to answer," he said.

Pressed by ABC News if U.S. officials have seen any proof of life, Kirby said, "I am not aware of any specific proof of live on any individual hostage."

6:09

Blinken heads to Israel to reiterate support amid conflict in Gaza

Secretary of State Antony Blinken is the first senior U.S. official to head to Israel since the conflict started.

Asked if the U.S. has had any communication with Hamas, directly or through allies, Kirby said, "We're in discussions not only with the Israelis about what hostage recovery can look like, but with other allies and partners in the region. And there are some countries like Qatar that have open lines of communication with Hamas. So, of course, we're casting the net wide."

"We haven't made any policy options or operational decisions with respect to hostage recovery at this time," he said.

Kirby said there is no "specific evidence that Iran was directly involved with these specific sets of attacks" on Israel, but he added, "We are going to keep looking at it -- the book is not closed."

In recent days, the White House has consistently said there was no evidence pointing to Iran’s participation but said Iran was broadly complicit with their past funding and support for Hamas.

-ABC News' Mary Bruce

Rep. Cory Mills, R-Fla., a freshman lawmaker and veteran who served in Iraq, has traveled to Israel and is working to help evacuate Americans through Jordan, a spokesperson confirmed to ABC News. News of his trip was first reported by The Floridian.

-ABC News' Ben Siegel and Lauren Peller