A strike by Iran on Israel is a "real and credible" threat, the White House has said, as fears of an imminent attack by Tehran grow, Ednews reports.
Tensions are high over the possibility Iran will retaliate for an air strike that killed senior Iranian commanders nearly two weeks ago.
US officials had told CBS News, the BBC's US partner, that a major attack on Israel could happen imminently.
Israel has said it is ready "defensively and offensively".
"I can't speak to the size, scale, scope of what that attack might look like," US National Security Council spokesman John Kirby said on Friday. But he added that the Iranian threat was "viable," saying Washington was "watching this very, very closely".
He said: "We are in constant communication with our Israeli counterparts about making sure that they can defend themselves against those kinds of attacks".
One US official CBS spoke to warned Iran could use more than 100 drones, dozens of cruise missiles and possibly ballistic missiles.
These would reportedly be aimed at military targets in Israel.
The official added that there was still a possibility Iran could decide to hold back.
President Joe Biden has already promised Israel his country's "ironclad" support in the event of an Iranian attack.
The mounting tensions have led countries including the US, UK, India and Australia to warn against travelling to Israel.
The US State Department also barred diplomatic staff and their families in Israel from travelling outside of the cities of Tel Aviv, Jerusalem and Beersheba.
On Friday, Israeli Prime Minister Benjamin Netanyahu met members of his war cabinet amid the warnings.
But some Israelis said they were not worried about a potential Iranian attack.
"We know that we are surrounded by enemies, in the south, in the north, the east and the west," Daniel Kosman said from a market in Jerusalem.
"We are not afraid, I can promise you. Look around: people are going out."
The possibility of an Iranian attack has led to concern and anxiety in Israel. But the government has not issued any new advice to the population on top of existing guidance to stock up on water, food for three days and essential medicine.
Israeli radio, however, reported local authorities had been told to prepare for the possibility of an attack, including by assessing the readiness of public shelters.
Last week, amid the first indications an Iranian response was possible, the Israeli military cancelled home leave for combat troops, bolstered air defences and called up reservists.
Thirteen people were killed in the 1 April missile strike on the Iranian consulate in the Syrian capital Damascus.
They included senior Iranian military leaders, among them Brig Gen Mohammad Reza Zahedi, a senior commander of Iran's elite Quds Force in Syria and Lebanon.
Israel has not commented, but is widely considered to have carried out the attack.
Officials in several countries have been trying to dissuade Iran from launching an attack on Israel, fearing it could spark a wider regional war.
