By Jill Serjeant

LOS ANGELES - Miley Cyrus, the teen sensation of Disney Channel's "Hannah Montana" hit TV show, is growing up, releasing a new album called "Breakout," and hoping her millions of young fans will come along for the ride.

"It's grown up. I wrote all the songs except two," said Cyrus, 15, of the new album, the first that does not play on her squeaky-clean "Hannah Montana" persona.

Set for release on Tuesday, the bubbly pop CD is expected to storm record charts in North America where Cyrus was the 16th biggest touring act in 2007, selling $36 million in tickets.

"Songwriting is what I really want to do with my life forever," Cyrus told Billboard magazine in a front-cover photo shoot and interview last month. "I just hope this record showcases that, more than anything, I'm a writer."

Cyrus shot to fame in 2006 as Hannah Montana - a girl who leads a double life as an ordinary teenager and a singing sensation. In two years, the popular character has become a merchandising sensation spawning record albums, a hit concert film, and an entertainment franchise valued by financial analysts at some $1 billion.

Even as she prepares to shoot a third series of the show, Cyrus seems to be looking to a future when she will have to leave behind her alter ego.

Teen idols - think David Cassidy in the early 1970s or 1980s boy band New Kids on the Block - have a brief shelf life.

"It is really difficult when your core audience is preteen because as those kids get older, what was beyond cool to them one moment, is something they won't even admit they were fans of three years later," said Gary Bongiovanni, editor in chief of the concert magazine Pollstar.

A disastrous Vanity Fair photo shoot in April, in which a tousled-haired Cyrus posed wrapped only in a bedsheet, illustrated the pitfalls of navigating that transition.

Cyrus raised eyebrows again last week by telling TV Guide she was a big fan of the steamy TV show "Sex and the City".

"I'd love to do a younger, cleaner version of 'Sex and the City'," she told TV Guide, referring to the future. "I like to think of myself as the girl that no one can get."

In the same interview, she listed the Bible as the top thing she could not live without and said she wore a purity ring, a symbol of her intention to avoid premarital sex.

Such apparent contradictions are unlikely to dent sales and Internet downloads of "Breakout."

"I think the same young girls who were eager to buy the first two albums will be just as eager to find out what she is doing with this album, even if she is trying to position herself more as a musician than an actress," said Geoff Mayfield, senior music analyst for Billboard.