U.S. Senate Majority Leader John Thune has suggested that the only way Donald Trump can serve a third term as President of the United States is through a constitutional amendment.

Trump had on Sunday insisted that he is “not joking” about seeking a third term in office.

He said: “No, I’m not joking. I’m not joking.

“There are methods which you could do it, as you know.”

A third term in office is barred by the U.S. Constitution, but Thune believes Trump can serve a third term if there is a change to the current Constitution.

However, when asked whether he believes Trump can serve a third term as U.S. President, Thune told reporters on Monday, as quoted by NBC News: “Not without a change in the Constitution.”

Thune then added that Trump doesn’t appear serious about seeking a third term.

“I think that you guys keep asking the question, and I think he’s probably having some fun with it, probably messing with you,” he added.

Senate Majority Leader reveals only way Trump can do third term as US president