WASHINGTON (AFP) - In his first interview since losing his 2012 White House bid, Mr Mitt Romney likened his experience as a presidential candidate to an unpredictable and bumpy roller coaster ride.

"We were on a roller coaster, exciting and thrilling, ups and downs. But the ride ends," Mr Romney said, according to advance excerpts of the interview set to air on Fox News Sunday.

"And then you get off. And it's not like, 'Oh, can't we be on a roller coaster the rest of our life?' It's like, no, the ride's over."

Mr Romney appeared with his wife Ann for the interview, the first either has given since the Nov 6 election that granted President Barack Obama his second term.

Mrs Ann Romney acknowledged that the transition from being surrounded by huge crowds and Secret Service agents around the clock to a far lower profile has been an "adjustment." "We came and stepped forward to serve," she added.

"It was really quite a lot of energy and a lot of passion and a lot of people around us and all of a sudden, it was nothing.

"But the good news is, fortunately we like each other."

Mr Romney, who has not had any major public appearances since his election loss, is set to speak in two weeks at a key conservative gathering, the Conservative Political Action Conference.

The former Massachusetts governor has been laying low since his defeat, popping up occasionally in photographs on social media sites that apparently depict him shopping or filling up his tank at the gas station.

When Senator John Kerry of Massachusetts left Congress to become secretary of state earlier this year, it opened up a race in his home state to fill his seat.

Speculation swirled that Mr Romney's oldest son Tagg might throw his hat in the ring, but he quickly ruled it out.

Romney aides have also rebuffed suggestions that his wife might consider running for the post.