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

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

If Israel strikes back, the response speed from Iran "will be less than a few seconds," said Ali Bagheri Kani, the deputy foreign minister of Iran for political affairs.

Maj. Gen. Pat Ryder, the Pentagon press secretary, said Monday that Iran did not give the U.S. an advanced notice of its attack on Israel.

"I think what you're asking was did Iran give us a heads up? No, they did not," Ryder said, without indicating whether the U.S. learned of Iran's plans through allies.

Ryder said U.S. forces in the Middle East intercepted dozens of missiles and unmanned aerial vehicles when Iran and its proxies launched attacks in retaliation for Israel's strike earlier this month on the Iranian Consulate in Damascus, Syria, that killed an Iranian military leader.

Ryder repeated assessments that 99% of incoming Iranian fire was intercepted by Israel and its partners, but he wouldn't confirm reports that half of the launches failed to get off the ground.

Secretary of Defense Lloyd Austin, Ryder said, has spoken with Israeli Defense Minister Yoav Gallant three times since the attack.

"During their most recent call yesterday, the two leaders reviewed the successful combined operation by the United States, Israel and their partners to defend Israel from these unprecedented attacks by Iran and its proxies and emphasize that while the United States does not seek escalation, we will continue to take all necessary action to defend Israel and U.S. personnel," Ryder said.

Asked whether the response to Iran's attack depleted the air defense resources of Israel and its partners, Ryder declined to answer.

"As we demonstrated this weekend, we have the capability and the capacity to defend Israel and to defend our forces in the region," he said.

-ABC News' Chris Boccia and Matt Seyler