The United States said Sunday it will not join any Israeli counterattack on Iran, with President Joe Biden warning Prime Minister Benjamin Netanyahu to "think carefully" about any escalation.

The White House said Biden did not want a wider war after helping key ally Israel repel a massive aerial attack by Tehran — itself in retaliation for a presumed Israeli strike that killed an Iranian general in Damascus.

"We're not looking for a wider war with Iran," White House National Security Council spokesman John Kirby said on NBC's "Meet the Press," adding that the United States does not "want to see this escalate."

Kirby said Netanyahu was "well aware" of Biden's feelings after the two leaders spoke on Saturday while Iran's unprecedented attack was still unfolding.

The assault saw Iran fire more than 300 drones and missiles towards Israel late Saturday, injuring 12 people, the Israeli army said.

US officials said American warplanes had brought down around 70 drones while US ships downed between four and six ballistic missiles.

But a senior Biden administration official confirmed that Biden had told Netanyahu that Washington would not offer military support for any retaliation on Iran.

"We would not be a part of any response they do," the official told reporters on a call, speaking on condition of anonymity. "We would not envision ourselves participating in such an act."

Washington — which is Israel's biggest military supplier and has also been pressing for an end to the conflict in Gaza — was also trying to guide it away from further escalation.

"A big question is not only whether, but what Israel might choose to do, and so this is a decision for them," the Biden administration official said.

'Carefully and strategically'

Biden and Netanyahu spoke at a time of "heightened emotion" while the attacks were still ongoing and "had a discussion about trying to slow things down."

The US president "made very clear to the prime minister last night that we do have to think carefully and strategically about the risks of escalation."

Israel was on high alert Sunday after Iran's unprecedented attack sparked fears of a broader conflict.

It marked a major escalation of the long-running covert war between the regional foes.

Almost all the Iranian drones and missiles were intercepted before they reached Israeli territory, the Israeli army said, with help from the United States, Jordan, Britain and other allies.

Kirby said it was an "incredible effort by Israel," he said, "but also it shows that Iran is not the military power weight that they claim to be." 

He added that the United States is "staying vigilant" to any Iranian threats to American troops. 

"We made it very clear to all parties, including Iran, what we would do ... and also how seriously we would take any potential threats to our personnel," Kirby said.

Continuing his round of the Sunday morning political talk shows with an appearance on CBS, Kirby elaborated: "We're going to take whatever steps we need to take to protect our troops, our ships, our facilities in the region going forward."

Kirby also stressed that negotiations between Hamas and Israel on a truce in Gaza and a hostage release deal were still underway.

"We're not considering diplomacy dead there," he said.

Kirby said CIA director Bill Burns negotiated a new deal in Cairo about a week ago that would "get dozens of the most at-risk women, elderly, the wounded out, get us a six-week ceasefire."

"The Hamas leaders need to take that deal. And we're not considering this dead at this point."