SAN FRANCISCO (AP) — Lyft still hasn't caught up to Uber in the rapidly growing ride-hailing market, but it's ahead in the race to sell its stock on the public market where the two companies could potentially raise billions to help finance their expansion.

The San Francisco company has taken the first step toward listing its shares on the U.S. stock market by filing confidential documents for an initial public offering. The filing, announced by Lyft Thursday, is expected to become publicly available early next year, a few weeks before Lyft's investment banks price the shares after gauging investor demand.

Both the IPO price and the number of shares that will be sold will be revealed leading up to Lyft's stock market debut.

Lyft's IPO is expected to generate intense interest while helping to set the stage for Uber to go public. Uber has already disclosed it will go public next year, but hasn't indicated when.

The two IPOs will give investors their first chance to buy stakes in the ride-hailing phenomenon that has transformed the way people get around, particularly in big cities.

The trend has already turned Lyft and Uber into prized investments even though the two have yet to prove they can make money. They have created vast networks of people using their own cars to give rides to passengers who summon them on smartphone apps. While the companies take in commissions from the ride fares, their spending has so far outpaced that revenue.

Lyft was valued at $15 billion after raising money from investors in the private markets, a figure that it probably will seek to increase in its IPO. Uber was recently valued at $76 billion, but may sell its shares at a price that would give it a $120 billion valuation in its IPO, according to a recent media report.

Getting a head start with its IPO will allow give Lyft a "first-mover advantage" over Uber and help steer investor expectations about the growth and moneymaking potential of ride-hailing services, said Rohit Kulkarni, managing director of SharesPost, which focuses on privately held companies going public.

Although Lyft still ranks a distant second, it has been gaining market share during the past two years as Uber faced a backlash following revelations of rampant sexual harassment within its ranks , a cover-up of a major computer break-in , allegations of high-tech thievery and a fatal collision involving one of its robotic cars.

The IPO is likely to generate a buzz that could attract more attention to Lyft, and make more people aware that it's a viable alternative to Uber.