US President Donald Trump said Wednesday the ceasefire with Iran was "over" after the two sides traded fire, but added that negotiators could keep talking to Tehran.
Trump blasted Iran as "scum" and "cuckoo" after Washington launched strikes on the Islamic Republic overnight and Iran's Guards said they had targeted US bases in the Gulf.
Oil prices jumped five percent after Trump's remarks.
"I think it's over. I don't want to deal with them any more, they're scum," Trump said at a NATO summit in the Turkish capital Ankara when asked if the truce with Iran was now finished.
"They're scum, they're sick people, they're led by sick people, and they're vicious, violent people. And if they had a nuclear weapon, they'd use it.
"As far as I'm concerned, it's over."
Trump said he would speak to businessman-turned-negotiator Steve Witkoff and his son-in-law Jared Kushner, who have been dealing with the Iranians, but insisted it was up to Tehran to return to the table.
"Frankly, I don't want to waste my time with them. Now, I'll let our wonderful negotiators keep talking if they want, but I don't see it," Trump said.
"As far as I'm concerned, it's just a waste of time dealing with them. They're liars."
Trump accused the Iranians of repeatedly misrepresenting what had been agreed in the ceasefire that Washington and Tehran signed on June 17.
"Everyone's agreed, no nuclear weapon. We make a deal. They go outside, joke to the press, they say we never even talked about it. There's something wrong with them, they're cuckoo," Trump added.
NATO chief Mark Rutte, with whom Trump was meeting when he made the comments, backed the US strikes on Iran.
"I think what you did last night was absolutely necessary. It was a very strong response, and I'm with you on this," Rutte told reporters.
But despite Rutte's efforts to placate Trump -- whom he called "Daddy" at a NATO summit last year -- the US leader again hit out at NATO for failing to get involved in the Iran war.
"I'm not happy with NATO because of the fact that they didn't want to help us with the number one state sponsor of terror, that's Iran. They were unwilling to help us," Trump said.
"I spoke with UK, and the prime minister said, 'well, we don't want to help you now, but we'll help you when the war is over.' I said that's not good. And likewise, I spoke to Germany, they didn't want to help. Spoke to France, didn't want to help."
The US military said it had struck over 80 targets including Iranian speedboats in response to Iranian attacks on ships in the vital Strait of Hormuz.