He said his "greatest fear" was that Tehran had a nuclear weapon which would give it a "stranglehold" on Israel and the rest of the world.

"When it comes to NATO's stance on Iran's nuclear programme, allies have long agreed that Iran must not develop a nuclear weapon," said Rutte ahead of a NATO summit in The Hague.

He dismissed suggestions that the war in the Middle East would deflect attention from the summit of the 32 NATO leaders starting on Tuesday.

Rutte also noted that Iran was "heavily involved" in Russia's war against Ukraine.

"Iranian drones are killing innocent Ukrainians every day in cities, in communities without any respect for life," said Rutte.

Over the weekend, President Donald Trump said US warplanes had used "bunker buster" bombs that had "obliterated" Iran's nuclear capabilities.

Other officials said it was too soon to assess the true impact on Iran's nuclear programme, which Israel and some Western states consider an existential threat.

Iran has warned the US bombing would "pave the way for the extension of war in the region" and threatened "serious, unpredictable consequences".

As the world awaited Iran's response, supreme leader Ayatollah Ali Khamenei called the bombing campaign Israel launched on June 13 "a big mistake".

Israeli strikes on Iran have killed more than 400 people, Iran's health ministry said. Iran's attacks on Israel have killed 24 people, according to official figures.

"Let's focus on the essentials here. My biggest fear would be for Iran to own and be able to use and deploy a nuclear weapon to build a stranglehold on Israel, on the whole region and other parts of the world," Rutte said.

Pressed over the legality of Washington's strikes against Iran, the NATO chief replied: "I would not agree that this is against international law, what the US did."