Hamas said its holding between 200 and 250 hostages. Hamas said, "We will release detainees of different nationalities when the means of doing so are available on the ground."

Israel has said 199 hostages were taken.

Roughly 2,000 U.S. troops have been put on a heightened state of readiness for possible deployment to the Middle East, a Pentagon official said Tuesday morning.

The statement from deputy press secretary Sabrina Singh also says Defense Secretary Lloyd Austin has extended the deployment of the USS Ford carrier strike group, which was coming to the end of a planned six-month deployment to Europe.

The Ford CSG was sent to the eastern Mediterranean after the Hamas terror attack on Israel as a deterrent to Iran and its proxies. It will be joined by the USS Eisenhower CSG.

"No decisions have been made to deploy any forces at this time. The Secretary will continue to assess our force posture and remain in close contact with allies and partners," the statement said.

Overnight Israeli air raids killed at least 71 people and injured at least 50 others, the Palestinian Health Ministry said.

The strikes included attacks on Rafah, near a border crossing controlled by Egypt, and three homes that were bombed in Khan Younis in southern Gaza, official said.

The Israel Defense Forces says it hit Hamas targets.

Khan Younis is an area where the Israeli army has been urging people from northern Gaza to flee to. The border crossing in Rafah has seen thousands of people gather, waiting to cross into Egypt.

-ABC News’ Edward Szekeres

Israel Defense Forces said Tuesday morning it had "attacked over 200 military terrorist infrastructures of" Hamas throughout the Gaza Strip.

The IDF said it hit targets including a bank used by Hamas to "finance terrorism in the Gaza Strip." Also attacked were underground tunnels, warehouses that IDF said contained weapons and “operational headquarters in the center of Gaza City."

-ABC News’ Ellie Kaufman

In remarks with Israeli Prime Minister Benjamin Netanyahu, Secretary of State Antony Blinken said at least 25 Americans had now been confirmed dead in Israel.

Netanyahu described some of the atrocities committed by Hamas.

"Hamas has shown itself to be an enemy of civilization: The massacring of young people in an outdoor music festival, the butchering of entire families, the murder of parents in front of their children and the murder of children in front of their parents. The burning of people alive, the beheadings," he said.

"Hamas should be treated exactly the way ISIS was treated," he said. "They shouldn't be spit out from the community of nations. No leader should meet them. No country should harbor them. And those that do should be sanctioned."

Blinken said he was speaking not only as an American diplomat, but as a Jew, a husband and a father of young children, saying it was impossible for him to look at photos of families killed "and not think of my own children."

"The same time that we've been shocked by the depravity of Hamas, we've also been inspired by the bravery of Israel citizens," he said. "The grandfather who drove over an hour to a kibbutz under siege, armed only with a pistol and rescued his kids and grandkids. The mother who died shielding her teenage son with her body, giving her life to save his -- giving him life for a second time."

Blinken remarked that some U.S. aid had already been delivered, and that more military aid was on his way. He said the administration would work with Congress to meet Israel’s additional needs and that bipartisan support for Israel was "overwhelming."

The secretary called on world leaders to condemn Hamas.

Blinken also reiterated that Israel "has the right -- indeed, the obligation -- to defend itself" but that it was "so important to take every possible precaution to avoid harming civilians."

-ABC News' Shannon Crawford