Israel Defense Forces spokesman Rear Adm. Daniel Hagari said Israel focused too intensely on the Iranian nuclear threat at the expense of its ballistic threat.

A senior U.S. official told ABC News the U.S. also relied too heavily on the misguided conception that Iran's Supreme Leader Ayatollah Ali Khamenei was cautious and would never order a direct attack on Israel, and that this weekend’s attack and the general U.S. assessment of Iran now requires study and reassessment.

Sima Shine, a former head of the Iran desk at Israeli espionage agency Mossad, also said Israel’s assessment was wrong, and said "the rules of the game" have changed. A huge barrage of missiles was considered possible, but highly unlikely, Shine said.

Shine said any Israeli response under the new conception requires the assumption that Iran will follow up with its threat of another salvo of missiles. That said, Shine believes that Iran and the supreme leader do not want a full-scale war because it would be unpopular in Iran and the U.S. could get involved.

-ABC News’ Matt Gutman

Treasury Secretary Janet Yellen is warning Iran that the U.S. "will not hesitate" to impose new sanctions in response to Iran's "unprecedented attack" on Israel.

"Treasury will not hesitate to work with our allies to use our sanctions authority to continue disrupting the Iranian regime’s malign and destabilizing activity," Yellen is expected to say at a Tuesday press conference. "The attack by Iran and its proxies underscores the importance of Treasury's work to use our economic tools to counter Iran's malign activity."

Yellen's message follows President Joe Biden's Sunday meeting with the G7 nations, during which the leaders discussed a coordinated effort on sanction measures.

-ABC News’ Justin Ryan Gomez

Prime Minister Benjamin Netanyahu's war cabinet is expected to meet again on Tuesday to consider an Israeli response to Iran's weekend attack.

"We are closely assessing the situation. We remain at our highest level of readiness," Herzi Halevi, chief of staff of the Israel Defense Forces, said on Monday. "Iran will face the consequences for its actions."

Halevi added Israel would "choose our response accordingly."

-ABC News' Morgan Winsor and Somayeh Malekian

United Nations officials called on Tuesday for Israel and Iran to de-escalate their conflict, saying the retaliatory military attacks “violate the right to life and must cease immediately.”

“All countries are prohibited from arbitrarily depriving individuals of their right to life in military operations abroad, including when countering terrorism,” the U.N.’s Office of the High Commissioner for Human Rights said in a press release, quoting U.N. officials described as "experts."

The retaliatory strikes by both countries may constitute the “international crime of aggression by civilian and military leaders responsible,” those officials said, according to the statement.

-ABC News' Kevin Shalvey

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."