President Joe Biden said Tuesday in an address to the American people, "We stand with Israel. And we will make sure Israel has what it needs to take care of its citizens -- defend itself and respond to this attack."

Biden stressed, "Hamas does not stand for the Palestinian people's right to dignity and self-determination. Their state of purpose is the annihilation of the state of Israel on the murder of Jewish people. They use Palestinian civilians as human shields. Hamas offers nothing but terror and bloodshed, with no regard to who pays the price."

Biden said among the horrors were "parents butchered, using their bodies to try to protect their children. Stomach churning reports of being babies being killed. Entire families slain. ... Women raped, assaulted, paraded as trophies."

"There's still so many families desperately waiting to hear the fate of their loved ones, not knowing if they're alive or dead or hostages," Biden said. "Infants in their mother’s arms, grandparents in wheelchairs, Holocaust survivors abducted and held hostage. Hostages whom Hamas has now threatened to execute in violation of every code of human morality."

"It's abhorrent," Biden said, adding that Hamas' "brutality ... brings to mind the worst rampages of ISIS. This is terrorism. But sadly, for the Jewish people, it's not new."

Biden and Vice President Kamala Harris spoke with Israeli Prime Minister Benjamin Netanyahu earlier in the day.

Biden said, "We're surging additional military assistance, including ammunition and interceptors, to replenish Iron Dome. We're going to make sure that Israel does not run out of these critical assets to defend its cities and its citizens. My administration has consulted closely with Congress throughout this crisis, and when Congress returns, we're going to ask them to take urgent action to fund the national security requirements of our critical partners."

"This is a moment for the United States to come together, to grieve with those who are mourning," Biden said, adding, "There is no place for hate in America -- not against Jews, not against Muslims, not against anybody."

At least 14 Americans have been killed in the Hamas terrorist attacks in Israel, President Joe Biden said Tuesday in an address to the American people.

He condemned Hamas' incursion as an "act of sheer evil."

Biden confirmed that American citizens are among those being held by Hamas.

He said he's directed his "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."

The families of 155 Israeli soldiers have received death notices so far, the Israel Defense Forces said.

The U.S. has started reaching out to the families of Americans missing in Israel as part of its efforts to identify the U.S. citizens who may be among the hostages taken to Gaza by Hamas, according to an official.

But due to the dynamic situation and lack of visibility inside Gaza, the U.S. still can't say how many may be detained.

There's also a level of reluctance from U.S. officials to shine a spotlight on any Americans among the hostages for fear that they might be singled out by their Hamas captors.

Other sources said American officials are working the phones with allies in the Middle East who have leverage over Hamas, encouraging them to pressure the militants to free the hostages.

-ABC News' Shannon Crawford

In his first on-camera comments about Israel’s evacuation request for northern Gaza, Israeli Defense Minister Yoav Gallant urged Gaza residents to head south. He noted that Hamas will use them as "camouflage," “therefore we need to separate them."

"Those who want to save their life, please go south. We are going to destroy Hamas infrastructures, Hamas headquarters, Hamas military," he said.

Defense Secretary Lloyd Austin, who appeared at the press conference with Gallant, dodged ABC News' question about how Israel could end the Hamas terror threat without inevitably risking civilian lives. Austin called Israel's military "professional" and "disciplined."

Austin described how ISIS had also embedded themselves in civilian populations and how the anti-ISIS coalition "protected civilians and created corridors for humanitarian movement even in the midst of a pretty significant fight. So again, this is a professional force. It is well led, and I have every expectation that it will be disciplined."

Austin added, "I would tell you that in countering ISIS, I felt as if we were staring evil in the eye, it was truly evil. And what we've seen from Hamas, it takes that evil to another level."

-ABC News' Matt Seyler and Luis Martinez