WASHINGTON (AP) — President Joe Biden on Wednesday condemned the weekend attack by Hamas militants on Israel as the deadliest day for Jews since the Holocaust as the number of US citizens killed in the fighting ticked up to at least 22.

“This attack was a campaign of pure cruelty — not just hate, but pure cruelty — against the Jewish people,” Biden told Jewish leaders gathered at the White House.

Beyond the 22 known to have been killed, the State Department said at least 17 more Americans remain unaccounted for in a war that has already claimed more than 2,200 lives on both sides. A “handful” of US citizens are among the estimated 150 hostages captured by Hamas militants during their shocking weekend assault on Israel, White House national security spokesman John Kirby said Wednesday.

Signs of US support for Israel were seen across the administration, with Secretary of State Antony Blinken traveling there for meetings, Biden denouncing antisemitism in America and the US military moving a second aircraft carrier toward the Mediterranean Sea as part of efforts to prevent the war from spilling over into a more dangerous regional conflict.

Kirby said the USS Dwight D Eisenhower and its ships would be an “available asset” if necessary. The USS Gerald R. Ford, the Navy’s most advanced aircraft carrier, and its strike group have already arrived in the Eastern Mediterranean.

The attack has raised questions about the role of Iran, the main sponsor of Hamas, and whether it was directly involved in the operation. But the US has collected information that suggests senior Iranian government officials were caught off guard by the multipronged assault, according to a US official who wasn’t authorised to discuss the matter publicly and spoke on condition of anonymity. That piece of intelligence has informed White House officials publicly asserting that it has not yet seen evidence of direct involvement by Iranians in the planning or execution of the Hamas attack.

“We haven’t seen anything that tells they have specifically cut checks to support this set of attacks, or that they were involved in the training. And obviously, this required quite a bit of training by these terrorists,” Kirby said, though he added that the US will continue to look at the intelligence “and see if that leads us to different conclusion.”

Biden at the roundtable with Jewish leaders suggested the deployment of US military ships was a not-so-subtle message to Iran and other actors in the region. “We made it clear to the Iranians: Be careful.”

In Israel, Prime Minister Benjamin Netanyahu joined with a top political rival to create a war-time Cabinet, establishing a degree of unity as the government there faces public pressure to topple Hamas. Israel continued destructive airstrikes in Gaza, where a potential ground offensive would likely result in a large number of casualties on both sides of the conflict.

With many airlines suspending commercial flights in and out of Israel because of the ongoing rocket and missile exchanges, Kirby said the United States was exploring “a range of other options” to assist Americans who want to leave, appearing to leave open the possibility of a US-assisted evacuation.

Kirby said the administration was still in talks with Israel and Egypt to try to arrange safe passage for Gaza’s civilians. “These people are victims, too,” he said. “They didn’t ask Hamas to do this.”

Speaking to reporters on Wednesday morning, Biden sought to connect the Hamas attacks directly to decades of antisemitism and violence endured by Jews around the world.

“This attack has brought to the surface the painful memories and scars left by a millennium of antisemitism and genocide against the Jewish people,” Biden said. “We have to be crystal clear: There is no justification for terrorism, no excuse and the type of terrorism that was exhibited here is just beyond the pale, beyond the pale.”

Biden said he and Vice President Kamala Harris spoke by phone on Wednesday with Netanyahu. It was at least the fourth call between Biden and Netanyahu since Saturday’s attack.

“The United States has Israel’s back and we’re going to be working on this through the day and beyond,” Biden said.

Later in the day, while addressing Jewish leaders at the White House, Biden said he had tasked homeland security and law enforcement leaders “to work intensively with our Jewish community partners.”

“We’re also going to condemn and combat antisemitism at every single turn, every turn,” Biden said. “The past few days have been a solemn reminder that hate never goes away.” It can go underground, he said, but it doesn’t go away.