Motor racing-Patrick not returning to Stewart-Haas Racing

Sept 12 (Reuters) - Danica Patrick said on Tuesday she would not return to Stewart-Haas Racing in 2018 due to a new sponsorship arrangement for the team next season that leaves her future in the sport in doubt.

The announcement by Patrick, one of NASCAR'S most high-profile drivers, came shortly after Smithfield Foods said it would leave Richard Petty Motorsports to become a primary sponsor at Stewart-Haas next year.

"It has been my honor to drive for Tony Stewart, Gene Haas and everyone at Stewart-Haas Racing for the past six seasons," Patrick wrote on her Facebook page. "My time driving for them, however, has come to an end due to a new sponsorship arrangement in 2018."

There had been plenty of speculation that Patrick, who had lost her primary sponsor at the start of 2017, would not be able to fulfill sponsorships heading into the 2018 season.

She is now among a number of drivers, including current playoff contenders Kurt Busch and Matt Kenseth, who have yet to secure a firm contract to drive next season.

Patrick, 35, is still searching for her first top-five finish after five seasons behind the wheel of the No. 10 Ford.

Of her seven top 10s, Patrick's best result was sixth at Atlanta Motor Speedway in 2014. Her sole pole came in the 2013 Daytona 500.

In 180 races, Patrick has led 64 laps and has 71 lead-lap finishes. Her best finish in the final Cup standings was 24th twice (2015 and 2016).

Patrick was initially backed by Internet domain name service GoDaddy from 2007 with Andretti Autosport in the Verizon IndyCar series until 2015 in the Monster Energy NASCAR Cup Series with Stewart-Haas Racing.

GoDaddy, citing changing business objectives, eventually ended its racing sponsorships and Patrick then acquired fig bar purveyor Nature's Bakery as a primary sponsor in 2016. But they ended a three-year deal after one season following the 2016 campaign.

"Sponsorship plays a vital role in our sport, and I have been very fortunate over the course of my career, but this year threw us for a curve," said Patrick.

"Right now, my focus is on the remainder of the 2017 season and finishing the year strong. I have the utmost faith in myself and those around me, and feel confident about my future." (Reporting by Frank Pingue in Toronto; Editing by Clare Fallon)