President Joe Biden is expected to deliver remarks Tuesday at 1 p.m. ET from the White House, three days after Hamas fighters launched a surprise attack on Israel, prompting the two sides to engage in an ongoing war.

Israel’s military on Tuesday claimed to have regained control inside the country after it ordered a “full siege” of Gaza, meaning that no food, gas or power would be allowed into the densely populated area, Defense Minister Yoav Gallant said.

Fears have grown over the hostages that Hamas fighters took as it raised southern parts of Israel after the militant group threatened to start executing hostages if Israel bombs civilian targets in Gaza.

The exact number of hostages taken by Hamas fighters is unknown. No Americans have been confirmed to be among the hostages, but U.S. National Security Counsel spokesman John Kirby said that a number of Americans are unaccounted for and that it’s possible that are among those being held hostage.

In a statement Monday, Biden said at least 11 Americans have been killed in the Israel-Hamas war and that “it is likely” that some Americans are being held hostage.

“We are seeing the immense scale and reach of this tragedy,” Biden said. “In this moment of heartbreak, the American people stand shoulder-to-shoulder with Israelis. We remember the pain of being attacked by terrorists at home, and Americans across the country stand united against these evil acts that have once more claimed innocent American lives. It is an outrage.”

The Biden administration has stated its support for Israel. In his statement, Biden said he reaffirmed to Israeli Prime Minister Benjamin Netanyahu that the U.S. would “continue to make sure Israel has what it needs to defend itself and its people.”

In support of Israel, the Biden administration is sending ships of the Navy’s USS Gerald Ford Carrier Strike Group to the eastern Mediterranean Sea, and officials plan to keep in place some F-16 and A-10 fighter jets that were previously scheduled to rotate out of the region, a U.S. official told NBC News. The move is intended to signal a message to “stand down,” an official said.

The death toll from the Israel-Hamas war has soared to more than 1,600 people as of Tuesday morning, three days after Hamas fighters launched surprise attacks on Israel, according to officials. More than 900 people died in Israel and at least 770 in Gaza, with over 6,000 people injured in Israel and Gaza, officials said.

Biden is expected to face competing pressures within and outside of the Democratic Party that will make it more difficult to keep his pledge to provide support for Israel’s plans to defend the country.