President Joe Biden says the weekend attack by Hamas militants on Israel was the deadliest against Jews since the Holocaust and called it a “campaign of pure cruelty.”

Biden made the remarks while speaking Wednesday with Jewish leaders as the U.S. said the number of U.S. citizens killed during the Hamas-Israel war had risen to 22.

A “handful” of U.S. citizens are among the roughly 150 hostages captured by Hamas militants during their shocking weekend assault on Israel, White House national security spokesman John Kirby said Wednesday.

In a further sign of U.S. support for Israel, Secretary of State Antony Blinken left for meetings with officials there. And the U.S. military is 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 U.S. has collected information that suggests senior Iranian government officials were caught off guard by the multipronged assault, according to a U.S. official who wasn’t authorized 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.