Pop star Britney Spears has beat the tabloids at their own game, dropping in on a taping of television's Late Show with David Letterman to announce that she was pregnant with her second child.

'Don't worry Dave, it's not yours,' the 24-year-old singer told the late-night talk show's host as she walked onto the stage in a black dress that revealed a tell-tale tummy bulge.

Her entrance was accompanied by the band playing My Prerogative, the title song on her greatest-hits album.

'Oh. Well, I think that's good news for both of us,' Letterman joked back.

The comedian went on to ask Spears point blank: 'So, we've established now that you are in fact pregnant, is that right?'

'Yes, sir,' she answered to wild applause from the studio audience.

Letterman then took Spears' hand and kissed it.

A spokesman for the CBS show says Spears' brief visit was a surprise to the studio audience that had been arranged earlier in the day.

Guests for network talk shows are usually booked weeks in advance.

Celebrity magazines and tabloids have speculated for weeks that Spears is expecting another child.

Spears married dancer Kevin Federline in September 2004 and gave birth to their first child, a son named Sean Preston, the following September.

The family lives in the beachfront enclave of Malibu, California, outside Los Angeles.

Federline has two other children by his former girlfriend, actress Shar Jackson.