The USS Eisenhower carrier strike group will move to the Eastern Mediterranean to join the USS Ford carrier strike group that arrived there earlier this week, a senior U.S. official and a U.S. official told ABC News.

U.S. officials have said publicly this week that the presence of the USS Ford carrier strike group in the Eastern Mediterranean was intended as a deterrent to Iran and Hezbollah, not to get involved in the Israel-Hamas conflict. The Eisenhower joining the Ford will increase the show of force enhancing that message of deterrence.

The Eisenhower strike group includes the aircraft carrier USS Eisenhower and the cruiser USS Philippine Sea (CG-58), and the destroyers USS Laboon (DDG-58), USS Mason (DDG-87) and USS Gravely (DDG-107).

The strike group left Norfolk, Virginia, on Saturday bound for a previously scheduled deployment that would take it to the Middle East via the Mediterranean Sea. While in the Mediterranean it was to have participated in previously-scheduled exercises in the U.S. European Command area of responsibility.

Earlier this week the Pentagon issued a statement that Defense Secretary Lloyd Austin would "continue to review both the Eisenhower and Ford’s deployment plans as he considers the appropriate balance of maritime capability across theaters in support of national security priorities."

-ABC News' Martha Raddatz and Luis Martinez

Twenty-nine Americans have been confirmed dead in Israel, according to a State Department spokesperson, up from 27.

Additionally, 15 U.S. citizens and one lawful permanent resident of the U.S. are still unaccounted for, the spokesperson said.

"State Department personnel have been in contact with their families," the spokesperson said in a statement. "The U.S. government is working around the clock to determine their whereabouts and is working with the Israeli government on every aspect of the hostage crisis, including sharing intelligence and deploying experts from across the United States government to advise the Israeli government on hostage recovery efforts."

-ABC News' Shannon K. Crawford

Defense Secretary Lloyd Austin spoke with Israeli Defense Minister Yoav Gallant on Saturday and “discussed the importance of adhering to the law of war, including civilian protection obligations, and addressing the worsening humanitarian crisis in Gaza while Israel continues its operations to restore security," according to the Pentagon.

President Joe Biden spoke on Saturday with Israeli Prime Minister Benjamin Netanyahu and Palestinian Authority President Mahmoud Abbas.

On Biden's call with Abbas, the president "reiterated that Hamas does not stand for the Palestinian people’s right to dignity and self-determination” and “offered President Abbas and the Palestinian Authority his full support for these important and ongoing efforts,” according to the White House.

The Israel Defense Forces said over the last few days its soldiers have fought Hamas terrorists in Israeli areas around the Gaza Strip and have since regained control of communities, evacuated the injured and taken Hamas fighters' weapons.

Now Israeli soldiers are "preparing to implement a wide range of operational offensive plans, which can include combined and coordinated strikes from the air, sea and land ... with an emphasis on significant ground operations," the IDF said.

Human Rights Watch has accused Israel of using white phosphorus munitions in military operations in Gaza on Wednesday, saying it violated international humanitarian law by putting civilians at unnecessary risk.

In a report released Thursday, Human Rights Watch said it based its determination on a video it said it has verified, as well as two eyewitness accounts.

The Israel Defense Forces said in a statement to ABC News that claims they used white phosphorus in Gaza are "unequivocally false."

ABC News geolocated a video showing a jellyfish-shaped plume of white smoke over the port of Gaza. The video was posted on Wednesday by the official Palestinian news agency WAFA and matches images posted on social media and by other news outlets on the day.

Two experts -- Amael Kotlarski, the weapons team manager for the defense intelligence firm Janes, and Amnesty International weapons investigator Brian Castner -- told ABC News that images suggested munitions deployed over the port of Gaza on Wednesday appeared to contain white phosphorus.

"We have verified that Israeli artillery forces striking Gaza are equipped with M825 and M825A1155mm white phosphorus projectiles," Castner told ABC News, pointing to photographs by an Anadolu Agency photographer taken on Monday and showing Israeli troops handling shells labeled "M825A1."

Kotlarski said visual evidence alone was not sufficient to confirm that these specific shells were used in the Gaza port strikes.

There are "perfectly legal" military uses for white phosphorus munitions, Kotlarski said, including to create a smoke screen to conceal movements, to mark targets for artillery or air strikes, or to illuminate a battlefield. However, its use in urban areas is "problematic due to the higher risk of collateral damage," Kotlarski said, including the munitions' potential to cause severe burns.

White House Principal Deputy Press Secretary Olivia Dalton said Friday the U.S. had not independently verified allegations Israel used white phosphorous "so that is not something I would want to speculate about or weigh in on at this time."

-ABC News' Christopher Looft, Ben Gittleson and Jordana Miller