US President Donald Trump on Monday ruled out running for vice president in the 2028 election but declined to definitively say he would not seek a third term, keeping alive speculation about how he might seek to extend his time in office.

Trump has repeatedly flirted with the idea of serving beyond the constitutionally mandated two terms, joking about it at rallies and teasing supporters with "Trump 2028" hats. Some allies have taken those signals seriously, suggesting that they are exploring legal or political pathways to make it happen – a possibility dismissed by most constitutional scholars.

The 22nd Amendment to the US Constitution bars anyone from being elected to the US presidency a third time.

Some supporters have suggested that one way around the prohibition would be for Trump to run as vice president, while another candidate stood for election as president and resigned, letting Trump again assume the presidency.

"I'd be allowed to do that," Trump said on Monday, in an exchange with reporters aboard Air Force One as he flew from Malaysia to Tokyo.

But he added: "I wouldn't do that. I think it's too cute. Yeah, I would rule that out because it's too cute. I think the people wouldn't like that. It's too cute. It's not – it wouldn't be right."

Scholars say Trump is barred from running for vice president because he is not eligible to be president.

The 12th Amendment to the US Constitution reads, "No person constitutionally ineligible to the office of President shall be eligible to that of Vice-President of the United States."

Referring to the possibility of a third term, Trump said: "I would love to do it. I have my best numbers ever."

When pressed by a reporter whether he was not ruling out a third term, he said, "Am I not ruling it out? I mean you'll have to tell me."

Asked about whether he would be willing to fight in court over the legality of another presidential bid, Trump responded, "I haven't really thought about it."

Trump on Monday also said Vice President JD Vance and Secretary of State Marco Rubio were "great people" who could seek the presidency in 2028.

"I think if they ever formed a group, it’d be unstoppable," he said. "I really do. I believe that."

Rubio, standing behind Trump in the plane cabin, chuckled and bowed his head sheepishly as Trump predicted a bright political future for him and nodded when Trump brought up Vance. (Reuters)