NEW YORK — The United States and Israel on Sunday at the United Nations Security Council (UNSC) strongly defended their military action targeting Iran's nuclear sites, saying the regime in Tehran cannot be allowed to have a nuclear weapon.

Their remarks came at the UN emergency meeting called by Iran in the wake of US-led strikes on three key Iranian nuclear sites on Sunday, prompting reactions from several UN member states.

"The time finally came for the United States in the defence of its ally and in the defence of our own citizens and interests, to act decisively", Dorothy Shea, the US representative to the UN Security Council. "The Iranian regime cannot have a nuclear weapon", she stressed.

Israel's envoy, in his remarks, praised the US for the targeted strikes on the Iranian facilities in Fordo, Natanz and Isfahan, warning that a nuclear-armed Iran spelt danger to the world.

"Make no mistake, the cost of inaction would have been catastrophic. A nuclear Iran would have been a death sentence, just as much for you as it would have been for us," Permanent Representative of Israel to the United Nations Danny Danon said.

The US military struck three sites in Iran early Sunday, entering into Israel’s effort to destroy Iran’s nuclear program in a gambit to weaken a longtime adversary said to be working towards a nuclear weapon.

The decision to directly involve the US comes after more than a week of strikes by Israel on Iran that have moved to systematically eradicate the country’s air defences and offensive missile capabilities, while damaging its nuclear enrichment facilities.

Iran vowed retaliation for the US strikes on its nuclear facilities.

"The timing, nature and scale of Iran's proportionate response will be decided by its armed forces", Amir Saeid Iravani, the permanent representative of Iran to the United Nations, told the UNSC, accusing Israel and the US of destroying diplomacy.

Tehran's key allies, Russia and China, strongly condemned the US military action. They proposed that the 15-member body adopt a resolution calling for an immediate and unconditional ceasefire in the Middle East.

UNSC members are expected to respond by Monday night. However, a resolution must have at least nine votes and not be vetoed by the US, the UK, France, Russia or China to pass.

At the session, UN Secretary-General Antonio Guterres called for a peaceful solution and diplomacy, saying, “We cannot – and must not – give up on peace.”

He urged immediate and decisive action to halt the fighting and return to “serious, sustained negotiations” on Iran’s nuclear program. He called for talks to find a verifiable solution with full access by UN nuclear inspectors and a restoration of trust.

In urging a return to diplomacy and a peaceful solution, Guterres stressed on Sunday that one path leads to wider war, while the other leads to de-escalation and dialogue. “We know which path is right,” he said. — Euronews