US Secretary of Defense Pete Hegseth has declared that America “does not seek war” with Iran in the aftermath of a surprise attack on three of that country’s nuclear sites.

The move marked the first time that the US had directly attacked Iran and prompted concerns about whether attacks could drag the US into a wider war. Hours later, Iran launched retaliatory strikes against Israel, causing damage in Tel Aviv. Late on Sunday (AEST), explosions were heard in Iran’s southwest city of Bushehr, the home of the nation’s only functioning nuclear power plant.

The American mission, called Operation Midnight Hammer, involved decoys and deception, and met with no Iranian resistance, Hegseth and Air Force general Dan Caine, chairman of the Joint Chiefs of Staff, said at a Pentagon news conference.

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“This mission was not and has not been about regime change,” Hegseth added.

That sentiment was echoed by Vice President JD Vance on NBC News’ Meet The Press.

“We’re not at war with Iran,” Vance said. “We’re at war with Iran’s nuclear program.”

Vance also declined to confirm with 100 per cent certainty that Iran’s nuclear sites were completely destroyed, saying instead that he believes the US has “substantially delayed” Iran’s ability to develop a nuclear weapon.

Hegseth, meanwhile, was more bullish, stating during the Pentagon briefing that “Iran’s nuclear ambitions have been obliterated”.

Caine said the goal of the operation — destroying nuclear sites in Fordow, Natanz and Isfahan — had been achieved.

“Final battle damage will take some time, but initial battle damage assessments indicate that all three sites sustained extremely severe damage and destruction,” Caine said.

Meanwhile, Iran cannot return to diplomacy while under attack by Israel and the United States, its top diplomat says, and will consult with Russia.

Iranian Foreign Minister Abbas Araghchi said he will fly to Russia, with whom Iran has a strategic partnership, for talks with President Vladimir Putin on Monday.

“The US showed they have no respect for international law. They only understand the language of threat and force,” Araghchi said in Istanbul, adding that Tehran has to respond based on its rights before diplomacy can be reconsidered.

Russia has “strongly condemned” the US attacks.

The “irresponsible decision” by the United States to bomb Iran violates international law and the United Nations Charter, the Russian Foreign Ministry in Moscow stated on Sunday.

The UN Security Council must respond to this, it said, adding that the attack has also harmed nuclear non-proliferation. Moscow said it therefore expects a clear response from the International Atomic Energy Agency.

Dmitry Medvedev, who serves as deputy head of President Vladimir Putin’s Security Council, said several countries were prepared to supply Tehran with nuclear weapons.

He didn’t specify which countries, but said the US attack caused minimal damage and would not stop Tehran from pursuing nuclear weapons.

- With AAP, CNN and NBC