Britney Spears is baffled and bemused by a property millionaire's bizarre claims he's engaged to the pop superstar.

Just weeks after the supposedly-single singer was romantically linked with a dancer on her Circus comeback tour, 40-year-old land developer John Sundahl claims he has been dating Spears on and off since they met in rehab in 2007, and the pair is planning a spring wedding in Germany.

The story originates from an interview Sundahl's personal pilot Lance Chase gave to the National Enquirer.

Chase told the tabloid, "Britney and John used to date, but they reconnected after her show in New Jersey, and now they're engaged. He got down on one knee in a Subway sandwich shop in Santa Monica (California) a week ago and proposed with a $4.5 million (?3 million) marquise-cut diamond. They plan on getting married at his aunt's farm in Germany in six weeks."

When approached by the New York Daily News to verify the story, Sundahl backed it up, saying, "Britney doesn't want to do anything until the tour is over. She wants press for her tour and not for an engagement."

But the wedding plans are news to Spears, who divorced second husband Kevin Federline in 2007.