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

Human Rights Watch has accused Israel of using white phosphorus munitions in military operations in Gaza on Wednesday, saying it violated international humanitarian law by putting civilians at unnecessary risk.

In a report released Thursday, Human Rights Watch said it based its determination on a video it said it has verified, as well as two eyewitness accounts.

The Israel Defense Forces said in a statement to ABC News that claims they used white phosphorus in Gaza are "unequivocally false."

ABC News geolocated a video showing a jellyfish-shaped plume of white smoke over the port of Gaza. The video was posted on Wednesday by the official Palestinian news agency WAFA and matches images posted on social media and by other news outlets on the day.

Two experts -- Amael Kotlarski, the weapons team manager for the defense intelligence firm Janes, and Amnesty International weapons investigator Brian Castner -- told ABC News that images suggested munitions deployed over the port of Gaza on Wednesday appeared to contain white phosphorus.

"We have verified that Israeli artillery forces striking Gaza are equipped with M825 and M825A1155mm white phosphorus projectiles," Castner told ABC News, pointing to photographs by an Anadolu Agency photographer taken on Monday and showing Israeli troops handling shells labeled "M825A1."

Kotlarski said visual evidence alone was not sufficient to confirm that these specific shells were used in the Gaza port strikes.

There are "perfectly legal" military uses for white phosphorus munitions, Kotlarski said, including to create a smoke screen to conceal movements, to mark targets for artillery or air strikes, or to illuminate a battlefield. However, its use in urban areas is "problematic due to the higher risk of collateral damage," Kotlarski said, including the munitions' potential to cause severe burns.

White House Principal Deputy Press Secretary Olivia Dalton said Friday the U.S. had not independently verified allegations Israel used white phosphorous "so that is not something I would want to speculate about or weigh in on at this time."

-ABC News' Christopher Looft, Ben Gittleson and Jordana Miller