By Naomi Tajitsu

DETROIT (Reuters) - Scion, Toyota Motor Co's youth-oriented brand, is targeting an older, more mainstream audience as "millennials" delay car purchases, raising the possibility of weaker-than-expected sales growth this year.

"Millennials are in fact buying cars, they have just waited longer to buy cars because they've come out of college with more financial debt than any other generation, so their decision making around durable goods is being delayed," said Andrew Gilleland, who took over as vice president of Scion in September.

He said the brand expected to sell 70,000 to 80,000 cars this year, acknowledging the risk that sales may come up short of a previous forecast of 80,000.

Scion is Toyota's solution-in-progress to an ongoing slide in car ownership among young drivers, who are increasingly turning to ride-hailing apps and car-sharing services as an alternative to owning cars.

Launched in 2003, the U.S. brand initially targeted drivers around the 18-35 age group, selling a small range of well-equipped, entry-level Toyota-made cars to millennials in hopes that they will graduate to the Toyota brand in the future.

Gilleland said roughly half of all Scion buyers were under 35.

They were no longer interested in quirky models including the compact xB that drove sales in the brand's early years, and were now interested in the iM four-door hatchback and iA four-door sedan.

"The customer is now very different from the people who were buying the xB, who wanted to stand out from the crowd," Gilleland said. "We've found that consumers are looking for something more mainstream now."

To win over a market in tune with hip hop, heavy metal and skateboarding, Scion has supplemented traditional car advertising with its own record label, online TV series and sponsored music events as it has tried to sculpt an image of an underground lifestyle brand.

But the strategy has been slow to generate lasting sales growth. Annual sales fell 3.2 percent to around 56,000 vehicles in 2015, marking a fifth consecutive year of decline, and are less than a third what they were in 2006, when sales peaked around 173,000.

Scion is counting on its first crossover model, the C-HR, which goes on sale in early 2017, as the brand bets on a general boom in U.S. demand for larger vehicles to lift sales to 100,000 next year.

(Reporting by Naomi Tajitsu; Editing by Leslie Adler)