Israel-Gaza updates: Biden speaks with Netanyahu about hostages' release, Gaza humanitarian assistance

The death toll resulting from Hamas’ initial attack had risen to 31 Americans killed and 13 still unaccounted for, said White House National Security Council spokesman John Kirby while aboard Air Force One Tuesday night.

Kirby also said President Biden will have a chance to "meet with some of the families. It'll be some of the families of those who have lost loved ones in Israel, and some of the families who still don't know the fate of their loved ones. And in fact, some of the family members, we expect, will also be family members of hostages that we know Hamas has taken."

-ABC News’ Ben Gittleson

The U.S. is planning is impose new sanctions on several Hamas leaders this week, according to a U.S. official.

The Treasury Department is planning to announce the sanctions this week, the official said.

Earlier Tuesday, a top Treasury official pledged that the agency would "bring our tools to bear against Hamas' financing and the overall funding of terrorism."

"Disrupting Hamas' financing operations is not new to us; this has been a priority for Treasury for decades," Under Secretary for Terrorism and Financial Intelligence Brian Nelson said at a news conference. "We are equipped to target this infrastructure and its supporters, whether they be political leadership, operatives, facilitators, financiers, investors, or entire global procurement networks."

Axios first reported this development Tuesday night.

-ABC News' Ben Gittleson and Elizabeth Schulze

President Joe Biden released a statement saying he was "outraged and deeply saddened by the explosion at the Al Ahli Arab hospital in Gaza, and the terrible loss of life that resulted."

"Immediately upon hearing this news, I spoke with King Abdullah II of Jordan, and Prime Minister Netanyahu of Israel and have directed my national security team to continue gathering information about what exactly happened. The United States stands unequivocally for the protection of civilian life during conflict and we mourn the patients, medical staff and other innocents killed or wounded in this tragedy," he said.

-ABC News' Ben Gittleson

The Biden administration is preparing a foreign aid package for $100 billion that will include assistance for Israel, two people familiar with the details told ABC News.

Details on the spending request were still being finalized ahead of an official request sent to Congress later this week, according to the sources.

The specifics of the aid package are now circulating among U.S. officials, according to sources.

One source told ABC News the "bulk" of the assistance will likely go toward Ukraine, while another person with knowledge of the proposal said the latest draft included $10 billion for Israel, as requested.

-ABC News' Anne Flaherty, Ben Siegel, and Allison Pecorin