US President Donald Trump said on Thursday that he would not use a nuclear weapon in the war against Iran.

“Why would I use a nuclear weapon? We've totally, in a very conventional way, decimated them without it,” Trump told reporters at the White House when asked whether he would use such a weapon.

“No, I wouldn't use it. A nuclear weapon should never be allowed to be used by anybody,” he added.

Asked how long he was willing to wait for a long-term peace deal with Iran, Trump said, “Don't rush me.”

He said Iran might have loaded up their weaponry “a little bit” during the two-week ceasefire, but added that the US military could knock that out in about one day.

“Their navy is gone. Their air force is gone, their anti-aircraft is gone ...maybe they loaded up a little bit during the two-week hiatus, but we'll knock that out about one day, if they did,” Trump added.

“I want to make the best deal. I could make a deal right now ... but I don't want to do that. I want to have it everlasting,” Trump said.