Washington (AFP)

The US attorney general said on Sunday that it would be "a heavy lift" for Donald Trump to find a legal way to run for a third term as president.

"I wish we could have him for 20 years as our president," Pam Bondi told Fox News Sunday, "but I think he's going to be finished, probably, after this term."

The US Constitution was amended in 1947 to set a two-year limit on the presidency, not long after Franklin Roosevelt died near the start of his fourth term in the White House.

But constitutional amendments require approval by two-thirds of both houses of Congress, as well as ratification by three-quarters of the 50 states, which political analysts say is extremely unlikely.

"That's really the only way to do it," Bondi said. "It'd be a heavy lift."

Trump's early talk of seeking a third term struck many as fanciful, but on March 31 the 78-year-old president told NBC News that he was "not joking" about the possibility.

He said there were "methods" that would allow it to happen.

The remarks by Bondi, a former Florida attorney general, about the difficulty of a legal third term appear to align with the views of most constitutional scholars.

But as a confirmed Trump loyalist holding the government's top law-enforcement office, her comments take on greater significance.

Earlier in the interview with Fox's Shannon Bream, Bondi spoke out against the broad legal pushback the still-young Trump administration has faced as he moves aggressively to put his policies in place.

"We've had over 170 lawsuits brought against us -- that should be the constitutional crisis right there," she said. "We'll continue to fight" those cases as they move through the courts.