The Israel Defense Forces said its fighter jets have killed Iman Nofal, a senior Hamas member who was a former leader of Hamas' military intelligence.

Gaza hospitals are estimated to have less than 24 hours of fuel left, according to the United Nations Relief and Works Agency.

President Joe Biden departs for the Middle East on Tuesday for in-person meetings with Israeli and Arab leaders amid concerns of an expanded conflict in the Israel-Hamas war.

National Security Council spokesman John Kirby told "Good Morning America" that Biden's focus is on the hostage situation, to make sure humanitarian aid can flow to civilians in Gaza, and to get an update from Israeli counterparts on their plans and ground operations.

Asked about safety concerns, Kirby said "there’s always a concern" wherever the president goes, and those concerns would be "appropriately addressed through the necessary force protection and personnel protection measures. "

Asked if Biden's visit also includes urging Israel to avoid a full-scale ground invasion of Gaza, Kirby reiterated that the U.S. is not telling the Israeli military how to operate but that civilians should be protected.

Kirby added that it's "vital" that the administration gets supplemental funding from Congress for Israel and Ukraine.

-ABC News' Justin Gomez

The Egyptian Food Bank has nearly 3,000 tons of aid, including food, medicine and blankets, ready to cross into Gaza to help its trapped residents, its CEO said. But for now, the trucks are sitting still as the Gaza-Egypt border remains closed.

Mohsen Sarhan, the CEO of the Egyptian Food Bank, told ABC News he went to the border on Tuesday morning.

"You can see people dying, like, few miles away from you," he said. "Everyone in the world knows that these people have run out of water, and they have run out of medicine and have they have run out of food. And you have all that right in front of you. And you can't give it to the people. It's a human rights crisis. And it's very frustrating."

-ABC News' Matt Rivers

As the Biden administration intensifies efforts to help American nationals leave Israel and Gaza, more than 20,000 U.S. citizens have reached out to the State Department asking for help in the wake of the Hamas attacks, including several hundred seeking to leave Gaza, according to two U.S. officials.

While not all have actively sought assistance with transportation, "many thousands" across Israel have indicated they needed help finding flights out of the country, the officials said.

Government-chartered planes have now started to ferry U.S. citizens from Israel to other countries in the region, though one official said the State Department still cannot share a detailed breakdown on the number of Americans whose departure it has already facilitated or the number of Americans still waiting for help "given this is an unfolding situation."

For Americans in Gaza, the U.S. is still eyeing the Rafah border crossing between Gaza and Egypt as a means of safe passage. Officials say they are very hopeful they will be able to work with Israel and Egypt to establish a corridor for U.S. citizens and other foreign nationals, but that it could take days to make substantial progress.

The Israeli government estimated that between 100 to 130 Americans were living in Gaza earlier this year. An official says the State Department believes hundreds more are visiting -- putting the total number in Gaza potentially between 500 and 600.

The State Department estimates that roughly 500,000 American citizens reside in Israel.

-ABC News' Shannon K. Crawford