President Joe Biden said he spoke with Jordanian King Abdullah II, members of the U.S. Congress and directed his national security team to remain in contact with their Israeli counterparts.

"I've also directed my team to remain in constant contact with leaders throughout the region including Egypt, Turkey, Qatar, Saudi Arabia, Jordan, Oman, UAE, as well as our European partners and the Palestinian Authority," Biden said.

President Joe Biden delivered remarks from the White House on Saturday expressing U.S. support for Israel in light of Hamas' attack.

"We will not ever fail to have their back," Biden said.

"Israel has the right to defend itself and his people full stop. There is never a justification for terrorist attacks and my administration's support for Israel security is rock solid and unwavering. Let me say this as clearly as I can. This is not a moment for any party hostile to Israel to exploit these attacks to seek advantage. The world is watching," Biden said.

Secretary of State Antony Blinken "reaffirmed" the U.S.' solidarity with Israel during a call with Israeli President Isaac Herzog and Foreign Minister Eli Cohen, a State Department spokesperson said.

"Secretary Blinken reiterated his condolences for the victims of the terrorist attacks against Israel and condemned those attacks in the strongest terms," the spokesperson, Matthew Miller, said in a statement. "Secretary Blinken also discussed measures to bolster Israel’s security. The Secretary underscored the United States' unwavering support for Israel's right to defend itself."

President Joe Biden is set to deliver remarks at 2:30 p.m. on the attacks in Israel from the State Dining Room, according to the White House.

-ABC News' Fritz Farrow

The United States is warning against other countries from becoming involved in the Israel-Gaza conflict amid fears that it could spread into a wider war in the Middle East.

"This is not the moment for other parties who are hostile to Israel to seek advantage or to seek to exploit the attacks that have taken place," Jon Finer, deputy national security adviser to U.S. President Joe Biden, Monday on "Good Morning America."

"That is part of why the United States has moved the Carrier Strike Group to the eastern Mediterranean to send a strong and unmistakeable signal that no one else should get involved in this," he added. "We'll see how things unfold in the course of the coming days."

Finer also emphasized that the U.S. believes "Israel has every right to defend itself full-stop."

"Israel will ultimately make the decisions about how it chooses to go about and conduct that defense," he said. "We are offering support in a number of ways."

Finer noted that "more U.S. steps to show support and solidarity for Israel" can be expected.

"The U.S. is going to offer support at every level for Israel's defense and we are working through details those details with our intelligence professionals, our military and our diplomats," he added. "We are in daily -- in fact, many times a day -- contact with Israeli counterparts to see what they need and offer it."

The U.S. "strongly suspect[s] that there will be American citizens among those killed" in the ongoing conflict, according to Finer.

"We are looking obviously very intensively into whether there were any Americans were among those who have been abducted and brought to Gaza. This is still ongoing," he said. "There is still fighting inside Israel as we speak and there is a bit of fog of war in terms of the ability to gather specific information. And so, we will have much more to say about this at the right time."

When asked for comment on a recent report by The Wall Street Journal that Iran was behind Hamas' latest attack on Israel, Finer responded: "We have no direct information to confirm that report. We've obviously seen it, we're looking into it, but we do not have the ability to corroborate it at this time."

"What we can be quite clear about is that Iran is broadly complicit in these attacks for having supported Hamas going back decades -- for having provided financial support, for having provided training, for having provided weapons to Hamas," he added. "What we don't have is direct information that shows Iranian involvement in ordering or planning the attacks that took place over the last couple days. It's something that we’re going to keep looking at closely."