Palm Beach, Florida - President Donald Trump said Sunday he envisages a four-week military operation against Iran, where American and Israeli strikes have killed the country's supreme leader and crippled its defense capabilities.

"It's always been a four-week process. We figured it will be four weeks or so," he told British newspaper the Daily Mail, the latest of several interviews with media outlets Sunday.

"As strong as it is, it's a big country, it'll take four weeks – or less," Trump said.

Earlier in the day, the Pentagon confirmed that three US service members were killed and five seriously wounded in the operation that Washington has branded "Epic Fury."

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Trump told NBC that American soldiers dying during strikes on Iran was to be expected in a war that was nevertheless a "great deal."

"We have three, but we expect casualties, but in the end, it's going to be a great deal for the world," he said.

According to Al Jazeera, at least 200 people have been killed in Iran, with more than 700 wounded amid the US-Israeli bombardment.

The deadliest incident so far was an attack on an Iranian girls' elementary school, which resulted in at least 148 casualties and 95 injuries.