President Biden on Tuesday confirmed that American citizens are among those being held hostage by Hamas in the wake of an unprecedented coordinated attack by the militant group over the weekend that killed more than a thousand people in Israel.

The president also said in remarks at the White House that the number of Americans killed in the attacks had risen to 14.

“We now know that American citizens are among those being held by Hamas,” Biden said.

“I’ve directed my team to share intelligence and deploy additional experts from across the United States government to consult with and advise Israeli counterparts on hostage recovery efforts,” he said. “Because as president, I have no higher priority than the safety of Americans being held hostage around the world.”

National security adviser Jake Sullivan told reporters that the U.S. does not know the number of hostages at this point, and the U.S. does not have information about their condition.

He added that the U.S. believes there are 20 or more Americans who are missing at this point, but that number is those who are currently unaccountable for and does not necessarily mean there are 20 or more American hostages.

U.S. officials previously warned it was likely that Americans are among those being held by Hamas but were working to confirm Monday. John Kirby, a White House spokesperson on national security issues, told reporters on a call Monday that there were still many Americans who are unaccounted for.

“So I can’t say definitely that we know Americans are being held hostage,” he said. “That said, we have to accept the grim possibility that some are.”

Biden added on Tuesday that he will call on Congress “to take urgent action” to provide funding to Israel.

“This is not about party or politics, this is about the security of our world, security of the United States of America,” he said.

Biden also called the attacks in Israel “an act of sheer evil” and said “we must be crystal clear, we stand with Israel.”

Updated at 3:02 p.m.