Israel-Gaza updates: 22, including 18 children, reported dead in Rafah strikes

Sources at the White House say there’s deep concern that an Iranian retaliatory strike against Israel -- and the possible Israeli response -- will widen this war.

President Joe Biden cut his weekend vacation short to consult with his national security team in preparation for this. They’ve been on high alert and knew this attack was imminent.

U.S. officials the military is prepared to provide assistance to defend Israel against attacks if needed.

The U.S. is already moving military assets to the region to deter Iran and help protect U.S. forces. Officials say they have been urging Iran against further escalation or attacks on U.S. forces. They’ve been stressing that the U.S. was not involved in the Damascus, Syria, strike earlier this month.

-ABC News' Selina Wang

Iran's leader has confirmed that a retaliatory attack on Israel has begun.

"The evil regime will be punished", Iran's Supreme Leader Ayatollah Ali Khamenei said in a statement on X.

Iranian state TV also confirmed the attack in a banner.

"The extensive drone operation of the Islamic Revolutionary Guard Corps against targets in the occupied territories has started a few minutes ago," the banner said.

A U.S. official has confirmed Israel's announcement that Iran’s retaliatory strike has begun.

President Joe Biden will meet with principals of the National Security Council to discuss events in the Middle East Saturday afternoon. The meeting will take place in the White House Situation Room, the White House confirmed.

"Iran has begun an airborne attack against Israel. President Biden is being regularly updated on the situation by his national security team," the White House said in a statement.

"This attack is likely to unfold over a number of hours. President Biden has been clear: our support for Israel's security is ironclad. The United States will stand with the people of Israel and support their defense against these threats from Iran," it added.

-ABC News' Luis Martinez and Mary Bruce

Iran has launched dozens of drones toward Israel, but it could take hours for them to reach, according to Israel Defense Forces spokesperson Daniel Hagari.

Israel is closing down its airspace after midnight local time and Israel's defense systems are deployed, according to Prime Minister Benjamin Netanyahu.

"We are prepared for any scenario, both in defense and attack," Netanyahu said in a video statement.

"The IDF is on high alert and is constantly monitoring the operational situation. The IDF Aerial Defense Array is on high alert, along with IAF fighter jets and Israeli Navy vessels that are on a defense mission in Israeli airspace. The IDF is monitoring all targets," the IDF said in a statement.

"We ask the public to adhere to and follow the instructions of the Home Front Command and the official IDF announcements regarding the matter," the statement added.