Police in New York, where there are locations sensitive to both Israeli and Palestinian interests, are adjusting patrols in response to the situation in Israel.

"The NYPD's Counterterrorism and Intelligence Division consistently work at a level of high alert. When events from around the world could possibly affect NYC or we get Intel on a threat to NYC, we always increase our presence around houses of worship and certain areas when these conflicts arise," the NYPD said in a statement.

The Beverly Hills Police Department also said it increased security and patrols around Jewish institutions in the City and continues to work closely with law enforcement partners in the region to ensure public safety.

Law enforcement and Homeland Security officials will be assessing the potential for residual violence in the U.S.

Increased security around Jewish facilities and on university campuses -- particularly where there is a history of confrontational interactions -- is to be expected. Increased attention is expected to be paid to potential cyber threats and online activities intended to inspire violence by Iran, Hezbollah and other extremists threat actors.

-ABC News' Aaron Katersky and Alex Stone

United Airlines, American Airlines and Delta Airlines announced they will suspend operations to Israel Saturday night following unrest in the region. After two departures scheduled for Saturday, United's future operations will be suspended until conditions allow them to resume, the airline said.

"The safety of our customers and crew is our top priority. We are closely monitoring the situation and we are adjusting flight schedules as required," the carrier told ABC News.

American Airlines said it will temporarily suspended operations to and from Tel Aviv and will continue to monitor the situation, adjusting its operations as needed.

"American Airlines has temporarily suspended operations to and from Tel Aviv, Israel (TLV) [Saturday] and [Sunday], and has issued a travel alert providing additional flexibility to customers whose travel plans are affected. We will continue to monitor the situation with safety and security top of mind and will adjust our operation as needed," American Airlines said in a statement.

Delta Air Lines has canceled scheduled flights in and out of Tel Aviv this weekend. The airline said its working to "safely transport Delta people back to the U.S. and will work with the U.S. government as needed to assist with the repatriation of U.S. citizens who want to return home."

-ABC News' Amanda Maile and Sam Sweeney

President Joe Biden spoke with Israeli Prime Minister Benjamin Netanyahu, telling him that the U.S. "condemns" Hamas' assault on Israel.

"I made clear to Prime Minister Netanyahu that we stand ready to offer all appropriate means of support to the Government and people of Israel. Terrorism is never justified. Israel has a right to defend itself and its people. The United States warns against any other party hostile to Israel seeking advantage in this situation. My Administration’s support for Israel’s security is rock solid and unwavering," Biden said in a statement.

Biden also extended his condolences for lives lost and wished those wounded a "swift recovery."

"My team and I are tracking this situation closely, and I will remain in close touch with Prime Minister Netanyahu," Biden said.

U.S. Secretary of State Antony Blinken issued a statement condemning Hamas' attack on Israel, saying the U.S. will "remain in close contact with our Israel partners."

"The United States unequivocally condemns the appalling attacks by Hamas terrorists against Israel, including civilians and civilian communities. There is never any justification for terrorism. We stand in solidarity with the government and people of Israel, and extend our condolences for the Israeli lives lost in these attacks," Blinken said in a statement.

-ABC News' Shannon Crawford

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."