By MJ Lee and Kevin Liptak, CNN

Washington (CNN) — President Joe Biden confirmed Tuesday that Americans are known to be among the hostages held by Hamas after its terror rampage over the weekend, and said the known number of Americans killed now stands at 14.

The president relayed the information during an afternoon speech from the White House, where he recounted in emotional terms the horrors of the attack.

Biden, who spoke earlier with Israeli Prime Minister Benjamin Netanyahu, offered his own view of what the country’s response might look like.

“I told him that if the United States experienced what Israel is experiencing, our response would be swift, decisive, and overwhelming,” Biden said from the State Dining Room.

The news of Americans among the hostages taken by Hamas since the attack began on Saturday confirms what had largely been assumed by administration officials but had not been confirmed until Biden’s speech. Biden’s national security adviser, Jake Sullivan, said later that the administration believes there are “20 or more Americans” believed to be missing from Israel Tuesday, but that that number does not necessarily reflect the number of hostages in Hamas custody.

Biden said during his speech that he was “directing 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, because as president, I have no higher priority than the safety of Americans being a hostage around the world.”

The president said he intends to ask Congress to approve more funding for Israel to help it defend its territory and people. He promised his administration would not allow Israel to run out of ammunition and interceptors for its Iron Dome air defense system, which is intended to shoot rockets out of the air before they strike Israeli territory.

“My administration has consulted closely with Congress throughout this crisis,” he said. “When Congress returns, I’m going to ask them to take urgent action to fund the national security requirements of our critical partners. This is not about party or politics, it’s about the security of our world, the security of the United States of America.”

But he also insisted any response must adhere to the rule of law, saying that is what differentiated Israel and the United States from the Hamas militants.

“Terrorists purposely target civilians, kill them. We uphold the laws of war. It matters. There’s a difference,” Biden said.

The remarks Tuesday were Biden’s most substantive since the outbreak of violence early Saturday. Within hours of the deadly Hamas attack on Israel that left hundreds of people dead, the president was on the phone with Netanyahu.

When Biden’s counterpart – reeling from one of the worst attacks on his country in decades – brought up the possibility of going into Gaza, the president did not warn him against doing so, a US official briefed on the conversation tells CNN.

That decision by the president – to hold back from urging Netanyahu to exercise restraint in the immediate aftermath of the attacks – in no small part reflects the sheer shock and breadth of Hamas’ brutal attack on Israel that makes this moment different, officials say.

“We are not urging restraint right now,” one official said.

The president and his national security team are keenly aware of what appears to be a growing likelihood of Israel making a ground incursion into Gaza. Over the past 72 hours, officials have acknowledged what a deeply tenuous position that possibility puts the administration in. As a general matter, the US has historically urged for a ceasefire on all sides when conflicts have broken out in the region.

The Biden administration has usually been very intent on handling those kinds of discussions very privately, and officials said this time will be no different. Biden’s first written statement over the weekend did not include the term “ceasefire” – an omission that struck current and former administration officials alike.

During his speech, Biden said the violence unleashed by Hamas was reminiscent of some of the worst attacks by ISIS in the previous decade.

“The brutality of Hamas, this blood-thirstiness, brings to mind the worst, the worst rampages of ISIS – this is terrorism, but sadly, for the Jewish people it’s not new,” Biden said. “This attack has brought to the surface painful memories and the scars left by millennia of anti-Semitism and genocide of the Jewish people, so in this moment, we must be crystal clear, we stand with Israel.”

Domestically, he said, law enforcement officials “have stepped up security around centers of Jewish life,” while “working closely with state local law enforcement and Jewish community partners to identify and disrupt any domestic threat that could emerge in connection to these horrific attacks.”

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