Donald Trump has described Israel's Friday morning attacks on Iran as "excellent" and warned Iran that things will get worse if the country does not agree to a nuclear deal with the United States.

Israel launched a huge attack on Iran in the early hours of Friday, targeting nuclear facilities, military commanders and scientists.

"I think it's been excellent. We gave them a chance and they didn't take it. They got hit hard, very hard. They got hit about as hard as you're going to get hit. And there's more to come. A lot more," Trump was quoted as saying by an ABC reporter.

Earlier on social media, Trump wrote: "I gave Iran chance after chance to make a deal. I told them, in the strongest of words, to 'just do it,' but no matter how hard they tried, no matter how close they got, they just couldn’t get it done."

Implying that he had been aware of the attacks ahead of time, Trump said that he told Iran that “it would be much worse than anything they know, anticipated, or were told”.