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

National Security Council spokesperson John Kirby avoided saying if the U.S. believed Israel's calls for civilians in Gaza to evacuate in the next 24 hours was possible but acknowledge that it was a "tall order" given how densely populated the area is.

"Well, I think we're going to be careful not to get into armchair quarterbacking the tactics on the ground by the IDF. What I can tell you is we understand what they're trying to do. They're trying to move civilians out of harm's way and giving them fair warning. Now, it's a tall order. It's a million people, and it's a very urban, dense environment, already a combat zone. I don't think anybody's underestimating the challenge here of affecting that evacuation," Kirby said in an interview on CNN Friday morning.

"But it's pretty clear that what they're trying to do is to the maximum extent possible avoid civilian casualties and also separate Hamas from the human shields. I mean, Hamas actually gave a counterorder telling Palestinians in Gaza to stay at home. Why? Because having human shields, they think, protects them," Kirby continued.

Asked about their efforts to secure a safe passage for civilians out of Gaza, Kirby reiterated that the U.S. is talking to Israel and Egypt but would not comment further on progress.

On the Rafah crossing specifically, Kirby said "So far it's still closed. But that doesn't mean were not going to still try as hard as we can to talk to the Israelis and Egyptians about getting it open and having some sort of safe passage out. It's important that we also continue to work to make sure that humanitarian assistance can get in. The United States has no intention of stopping our efforts to continue to deliver humanitarian assistance, but there has to be a path in, there has to be a path out."

Kirby had no update on the Americans who are believed to be held hostage in Gaza and could not confirm reports that 13 hostages have been killed by Israeli airstrikes, as Hamas has claimed.

-ABC News' Molly Nagle