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."

How did the world react?

Countries around the world condemned Iran's strikes on Israel, warning the attack could further destabilise the Middle East.

Here are some of the main reactions: 

United Nations

UN Secretary-General Antonio Guterres condemned "the serious escalation".

"I am deeply alarmed about the very real danger of a devastating region-wide escalation," he added, calling on parties to "avoid any action that could lead to major military confrontations on multiple fronts in the Middle East".

European Union

President of the European Commission Ursula von der Leyen called on Iran to "immediately cease" attacks, saying in a message on X, formerly Twitter, that "all actors must now refrain from further escalation and work to restore stability in the region".

Foreign policy chief Josep Borrell said the bloc "condemns in the strongest terms" the attack, calling it "an unprecedented escalation and a threat to regional security."

G7

The G7 group expressed its "full solidarity and support to Israel and its people and reaffirm our commitment towards its security", the group said in a statement following video talks.

"We demand that Iran and its proxies cease their attacks, and we stand ready to take further measures now and in response to further destabilising initiatives", it said.

NATO

NATO spokesperson Farah Dakhlallah said the military alliance condemned Iran's attack and is "monitoring developments closely", warning it is "vital that the conflict in the Middle East does not spiral out of control".

China

Beijing also urged restraint, calling the attack "the latest spillover of the Gaza conflict" and calling for the implementation of a recent UN Security Council resolution demanding a ceasefire.

"China calls on the international community, especially countries with influence, to play a constructive role for the peace and stability of the region," it added.

United States

US President Joe Biden promised "ironclad" support for Israel after holding an urgent meeting with top security officials.

"Our commitment to Israel's security against threats from Iran and its proxies is ironclad," Biden said on X, posting a picture of the meeting in the White House Situation Room.

White House National Security Council spokesman John Kirby said on NBC's "Meet the Press" later that "we don't want to see this escalate".

"We're not looking for a wider war with Iran", he said.

Britain

UK Prime Minister Rishi Sunak condemned the "reckless" strikes, which he said "risk inflaming tensions and destabilising the region". 

He called for "calm heads to prevail" and added Britain will "be working with our allies to de-escalate the situation".

Canada

Canadian Prime Minister Justin Trudeau said Ottawa "unequivocally condemns Iran's airborne attacks", adding: "We stand with Israel."

Egypt

Cairo expressed "deep concern" at the escalation of hostilities and called for "maximum restraint".

The foreign ministry also warned of the "risk of the regional expansion of the conflict", and added Egypt would be "in direct contact with all parties to the conflict to try and contain the situation".

France

French President Emmanuel Macron said on X: "I condemn in the strongest terms the unprecedented attack launched by Iran against Israel, which carries the risk of destabilising the region".

Germany

German Chancellor Olaf Scholz condemned the Iranian attack as "irresponsible and unjustifiable", his spokesman said. 

Foreign Minister Annalena Baerbock said the attack took the region to the "edge of a precipice".

Indonesia

Indonesia's foreign ministry said it was "deeply concerned" and called on the UN Security Council "to act immediately to de-escalate tensions and continue working towards lasting peace in the Middle East, including by ending the illegal occupation of Palestine and various violations of international law by Israel".

Iraq

Iraq's President Abdel Latif Rashid called for a "reduction of tensions", warned against the "spread of conflict" and emphasised "the need to stop the aggression against the Gaza Strip and to find a solution to the Palestinian question, given this is a fundamental element to the stability of the region".

Italy

Prime Minister Giorgia Meloni condemned the attack and said she feared "destabilisation of the region".

Qatar

Qatar expressed "deep concern" following the strikes and called on "all parties to halt escalation" and "exercise maximum restraint". 

The gas-rich emirate, which has been engaged in weeks of talks with Israel and Hamas, urged the international community to "take urgent action to defuse the tension and de-escalate."

Russia

Moscow expressed "extreme concern over the latest dangerous escalation in the region" and urged all sides to "show restraint". 

"We are counting on the regional states to solve the existing problems with political and diplomatic means," the foreign ministry said.

Saudi Arabia

The Saudi foreign ministry called on "all parties to exercise utmost restraint and spare the region and its peoples from the dangers of war".

It urged the UN Security Council "to assume its responsibility towards maintaining international peace and security".

South Africa

Pretoria, which has brought a lawsuit against Israel at the top UN court over its offensive against Hamas in Gaza, said it was "gravely concerned" over possible escalation of hostilities in the region.

"South Africa has continuously stressed that irrespective of whether states believe that their use of force is lawful, it is never wise to resort to war as inevitably, it is ordinary people who bear the brunt of conflict", its foreign ministry said in a statement.

Spain

Spanish Prime Minister Pedro Sanchez called for restraint, saying Madrid "will always condemn all forms of violence which threaten the security and the well-being of innocent civilians."

Syria

Syria Foreign Minister Faisal Mekdad told his Iranian counterpart in a phone call that "Iran's response... is a legitimate right to self-defence", according to state news agency SANA.

Turkey

Turkey's foreign ministry called on all sides to refrain from further escalation. 

"Israel's attack against the Iranian embassy in Damascus, contrary to international law, provoked our concern. The Iranian reprisal... showed yet again that events can quickly transform into a regional war", it said in a statement.

Ukraine

Ukraine President Volodomyr Zelensky condemned the attack, saying Iran's actions "threaten the entire region and the world, just as Russia's actions threaten a larger conflict".

"The obvious collaboration between the two regimes in spreading terror must face a resolute and united response from the world", he wrote on X.

Chile

Chile's President Gabriel Boric condemned the strikes, warning on X that "when tensions and crises between governments escalate into violence, it is always the people who pay."