The Israeli military says Iran has launched a number of drones towards Israel.
The army’s spokesman, Rear Admiral Daniel Hagari, said it would take several hours for the aircraft to arrive.
Speaking on Saturday evening, he said Israel was prepared.
Israel has been on heightened alert since an airstrike last week killed two Iranian generals in Syria.
Iran accused Israel of being behind the attack and vowed revenge.
Israel has not commented on that attack.
A US official briefed on the attack said Iran had launched “dozens” of drones.
The official could not publicly discuss details of the attack and spoke to The Associated Press on condition of anonymity.
President Joe Biden is being regularly updated by his national security team and is in constant communication with Israeli officials as well as U.S. partners and allies, National Security Council spokesperson Adrienne Watson said in a statement.
Earlier on Saturday, the Israeli military said it was cancelling school and limiting public gatherings to no more than 1,000 people as a safety precaution.
Briefing reporters, Mr Hagari said Israel is “prepared and ready” with defensive and offensive actions.
He also said there was “tight” co-operation with the US and other partners in the region.
The head of the US Central Command, General Erik Kurilla, has been in Israel in recent days to co-ordinate with Israel about the Iranian threats.
Israel has a number of layers of air defence capable of intercepting everything from long-range missiles to UAV’s and short-range rockets.
Mr Hagari said Israel has an “excellent air defence system”, but stressed it is not 100% effective and urged the public to listen to safety announcements.