Defense Secretary Lloyd Austin said Sunday he has ordered the Ford carrier strike group to sail to the Eastern Mediterranean to be ready to assist Israel after the attack by Hamas that has left more than 1,000 dead on both sides. Americans were reported to be among those killed and missing.

The USS Gerald R. Ford, the Navy's newest and most advanced aircraft carrier, and its approximately 5,000 sailors and deck of warplanes will be accompanied by cruisers and destroyers in a show of force that is meant to be ready to respond to anything, from possibly interdicting additional weapons from reaching Hamas and conducting surveillance.

The large deployment reflects a U.S. desire to deter any regional expansion of the conflict. But the Israeli government formally declared war Sunday and gave the green light for “significant military steps” to retaliate against Hamas.

Preliminary reports indicate that at least four American citizens were killed in the attacks and an additional seven were missing and unaccounted for, according to a U.S. official. The numbers were in flux and could change as a fuller accounting is compiled, according to the official, who spoke on condition of anonymity to discuss initial reports received by the U.S. Embassy in Jerusalem. Most, if not all, of those reported dead or missing are dual U.S.-Israeli citizens, the official said.

Read: More than 1,000 dead after surprise Hamas attack and Israel’s response

Along with the Ford the U.S. is sending the cruiser USS Normandy and destroyers USS Thomas Hudner, USS Ramage, USS Carney, and USS Roosevelt, and the U.S. is augmenting Air Force F-35, F-15, F-16, and A-10 fighter aircraft squadrons in the region.

“The U.S. maintains ready forces globally to further reinforce this deterrence posture if required,” Austin said in a statement.

In addition, the Biden administration “will be rapidly providing the Israel Defense Forces with additional equipment and resources, including munitions. The first security assistance will begin moving today and arriving in the coming days,” Austin said.

The Norfolk, Virginia-based carrier strike group( was already in the Mediterranean. Last week it was conducting naval exercises with Italy in the Ionian Sea. The carrier is in its first full deployment.

Read: US demands condemnation of Hamas at UN meeting, but Security Council takes no immediate action

Senior officials from the Pentagon and State Department briefed senators Sunday night, and Majority Leader Chuck Schumer said they were assured that the United States was giving Israel “everything they need.”

“I asked the representatives of our Defense Department if they are giving Israel everything they need, and I was heartened that they said yes and that they are surging support,” the New York Democrat said in a statement after the unclassified briefing.

“I asked them if they have denied any requests that Israel has made, and they said no. I urged them to ensure Israel has everything it needs to protect itself, and reiterated that the Senate stands ready to deliver on additional needs,” he said.

President Joe Biden and Israeli Prime Minister Benjamin Netanyahu, in a telephone call Sunday, discussed “the taking of hostages by Hamas terrorists, including entire families, the elderly, and young children,” according to a White House statement describing their conversation. Biden stressed that all countries “must stand united in the face of such brutal atrocities.”

The president updated Netanyahu on U.S. diplomatic efforts and said additional assistance for Israeli forces was on the way, with more to come in the days ahead, the White House said.

Read: Israeli and Palestinian supporters rally across U.S. as Israel declares war after Hamas attack

They also discussed ways “to ensure that no enemies of Israel believe they can or should seek advantage from the current situation.”

As part of the U.S. effort to deter further escalation, Secretary of State Antony Blinken spoke with his counterparts from Saudi Arabia, Turkey and the United Arab Emirates on Sunday. In each call, he encouraged each country's “continued engagement” and “highlighted the United States’ unwavering focus on halting the attacks by Hamas and securing the release of all hostages,” department spokesperson Matthew Miller said in separate statements on the three calls.

In the U.S. House, leaders of the Foreign Affairs Committee were preparing a bipartisan resolution that says it “stands with Israel” and condemns “Hamas’ brutal war.” The resolution is expected to be among the first items considered for voting once the House elects a new speaker.

“Now is the time to show the world the United States firmly stands with our friend and ally Israel in our condemnation of this heinous attack by Iran-backed terrorists,” said the committee chairman, Rep. Michael McCaul, R-Texas.

House business is currently at a standstill after the historic ouster of Speaker Kevin McCarthy, R-Calif.

Majority Republicans plan to kick off the selection process, in private, at a Tuesday evening forum where candidates can address their colleagues. The real contest could come as soon as Wednesday when the House next convenes.