WASHINGTON -- US President Donald Trump said Monday that the US military campaign against Iran has "capability to go far longer" than the four to five weeks he projected during media interviews one day earlier.

"We have capability to go far longer than that. We'll do it," Trump said at an event in the White House, referring to his earlier remarks that the attacks may last four to five weeks.

"I don't get bored. There's nothing boring about this," Trump said amid the war across the Middle East region.

Earlier, Trump told the New York Post that he is not ruling out sending US ground troops into Iran "if they were necessary".

A Reuters/Ipsos poll conducted Saturday and Sunday found that some 43 percent of US citizens disapproved of the strikes and just 27 percent approved.