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.

Starting Saturday night, the Jordanian airspace will be temporarily closed to all incoming, departing and transiting aircraft, Jordan's Civil Aviation Regulatory Authority said in a statement.

Hamas says it has handed Egyptian and Qatari mediators its response to an Israeli proposal it received at talks in Cairo last week, while reiterating its key demands of a permanent cease-fire, a withdrawal of Israeli forces from Gaza, the return of displaced people to their areas and places of residence and intensifying the entry of relief and aid.

"We also confirm our readiness to enter a serious and real prisoner exchange deal between the two parties," Hamas said in a statement.

-ABC News' Edward Szekeres

White House National Security Council spokesman John Kirby told ABC's "Good Morning America" Sunday that any response to Iran's Saturday night attack is up to Israeli forces.

But Kirby stressed that President Joe Biden does not want the situation to escalate or have the U.S. drawn further into any conflict.

When asked by ABC News' Whit Johnson about a response from Israel, Kirby said that it is up to the Israeli government to decide how to respond. He added that "the damage was extremely light," and the defenses in place proved Israel can defend itself.

"I won't speak for the Israelis. It's going to be up to them to decide whether and how they'll respond to this," Kirby said. "They showed last night, an incredible military capability on their own, but certainly in concert with friends."

When pressed about reports that Biden told Israeli Prime Minister Benjamin Netanyahu the U.S. would oppose a counterattack on Iran, Kirby said it was "not an accurate reading" of the president's message. He emphasized that the White House does not "want to see the situation escalate further."

"The president understands the prime minister runs a government for a sovereign state of Israel, and that they'll decide whether and how they're going to respond to what Iran did last night," Kirby said.

Kirby reiterated the White House's message that the president will do "whatever he has to protect our troops and our facilities, our people in the region." He said there is no current threat to U.S. service members and facilities, noting that more U.S. forces moved into the region after Oct. 7 to help defend Israel and shipping channels in the Red Sea.

"We're going to obviously be vigilant to any potential threat to our forces in the region," Kirby said. "But the president has been clear we are not looking for a wider war. We're not looking for a second front or a third front. We're not looking to see escalation and we're certainly not looking for a war with Iran."

Kirby added that good intelligence about the attack helped the U.S. and Israel prepare.

"We've been watching as closely as we could the intelligence picture, we had a pretty good indication of the size and the scale and the scope of what Iran was planning," Kirby said. "That is why, because we had a good sense of what they were going to do and with how much, we were able to really help Israel knock down almost everything that Iran threw at them."