PHOENIX (Reuters) - Danica Patrick, the only woman to win an IndyCar race, ended months of speculation about her racing future by announcing on Thursday that she will make a full-time move to NASCAR next year.

The petite American has divided her time between the two series for the past two seasons but had come under increasing pressure to commit to just one of the circuits to achieve more consistent results.

"I am going to race a full Nationwide schedule and a limited Sprint Cup schedule in my GoDaddy.com Chevrolet next season. The time is now. The opportunity is now."

A long-time darling of American motorsport, Patrick will compete in NASCAR's second-tier circuit, the Nationwide Series, for JR Motorsports, her current stock car team which is owned by Dale Earnhardt, Jr.

In the NASCAR Sprint Cup Series, she will be with Stewart-Haas Racing, co-owned by double Sprint Cup champion Tony Stewart and Gene Haas, founder of Haas Automation.

"Her work ethic is probably the best of anyone in the sport," Earnhardt Jr. said.

"People don't understand how difficult it is to do what she did -- racing two totally different cars at the same time. I'm glad she gets the opportunity to devote all of her attention to this car because I think she's going to continue getting better."

The photogenic Patrick, equally comfortable in front of the cameras as behind the wheel, became the only woman to reach Victory Lane in an IndyCar race with a win at Motegi in Japan in 2008.

However, she has made no secret of her preference to race on oval circuits rather than on street courses in recent years as IndyCar has increasingly focused on street tracks.

Patrick has recorded three top-10 finishes in seven starts this season in the Nationwide Series. Her best result was fourth in Las Vegas.

"I don't want to wait years," the 29-year-old said while sitting next to GoDaddy chief executive and founder Bob Parsons. "I want to do it now, and I'm lucky enough to have a sponsor that will stand behind me and allow me to go."

(Writing by Mark Lamport-Stokes in Los Angeles; Editing by Frank Pingue)