CNN
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The Biden administration is concerned that an attack from Iran is being planned following Israel’s killing of Hezbollah leader Hassan Nasrallah and is working with Israel on defense measures, a U.S. official said Sunday evening.

Joint defense measures are being prepared to deter an attack through changes in the U.S. military posture, the official added.

The Biden administration led a multinational defense of Israel in mid-April when Iran fired over 300 drones and missiles at Israel in response to the Israeli bombing of senior Iranian Revolutionary Guard officers in Syria.

The U.S. official declined to say what kind of attack is expected from Iran or what steps the U.S. military is taking.

Fears of a broader regional war in the Middle East have increased in recent weeks as Israel steps up its attacks on Hezbollah in Lebanon and the Iran-backed group vows to continue its fight even as more of its top commanders have been killed.

The Pentagon said in a statement Sunday evening: “Should Iran, its partners or its proxies use this moment to target American personnel or interests in the region, the United States will take all necessary measures to defend our people. “

Defense Department spokesman Gen. Patrick Ryder noted that there is “a significant amount of capability” in the region, including the USS Abrahm Lincoln Carrier Strike Group.

Nasrallah was killed in a massive Israeli bombing in southern Beirut on Friday. He led Iran’s most powerful proxy in the Middle East for decades, and his death is a potentially crippling setback for Hezbollah and a major blow to Iranian control in the region.

Biden administration officials are also defending their decision to announce the “breakthrough” of a ceasefire proposal between Israel and Hezbollah last week, which quickly turned into an embarrassment for the administration when Israeli Prime Minister Benjamin Netanyahu made it clear that Israeli forces would continue instead militant group would strike at the Lebanese.

US officials argue that Israel changed its mind on Wednesday evening after the proposal, which 11 other allies had signed, was announced. A US official said Israel had the ability to target Nasrallah.

The US official told CNN that the statement released by the US on Wednesday was approved by Israel after several days of joint work on it. In a hastily arranged call that evening, senior Biden administration officials confidently told reporters: “The ceasefire will last for 21 days” across the Lebanese-Israeli border.

They assumed it would take effect quickly so that diplomatic efforts could lead to a more permanent ceasefire.

But hours later, Netanyahu said Israel would “continue to attack Hezbollah with all its might.”

Israeli officials tried to explain the incident as an “honest misunderstanding.”

They said they thought what the U.S., France and other countries proposed was “the beginning of a process that could ultimately lead to a ceasefire.”

But “the Americans thought it was the end of the process and the beginning of a ceasefire,” a senior Israeli official told CNN.

What gave American officials confidence was the fact that they were dealing directly with one of Netanyahu’s closest associates, Ron Dermer. He and US national security adviser Jake Sullivan began talks two days earlier, on Monday.

The US official claimed on Sunday that the government backed away from enforcing last week’s ceasefire plan when it learned that Israel might try to take out Nasrallah. But the White House insists that efforts to find a diplomatic solution to return tens of thousands of Lebanese and Israeli civilians to their homes are still alive.

“I think we agree that there needs to be a de-escalation effort here,” White House national security spokesman John Kirby told CNN on Sunday.

“We believe and continue to believe that an all-out war with Hezbollah, let alone Iran, is not the right path. If you want to bring these people home safely and sustainably, we believe a diplomatic route is the way to go,” he added.