July 18 (Reuters) - America's 2006 MotoGP world champion Nicky Hayden announced on Thursday that he would be leaving the factory Ducati team at the end of the season.
"I'm not coming back to Ducati in MotoGP next year - I'm not really sure what I'm going to do," he said in a U.S. Grand Prix news conference at Laguna Seca, California.
"I've got some options that are interesting," added the Kentucky-born rider.
Asked whether he hoped to stay in MotoGP or was looking at other categories, Hayden added: "Of course MotoGP is where my heart is, but I've got to weigh up the options. Unfortunately results haven't gone as planned over the years, but it is what it is."
Hayden, who won his title with Honda, is ninth in the championship with 57 points after eight of 18 races and is out of contract at the end of the year. Italian team mate Andrea Dovizioso is sixth with 74.
The 31-year-old American moved to Ducati in 2009 and has not won a race since 2006.
Britain's Cal Crutchlow, who is having a great season on the non-works Tech3 Yamaha and is fourth in the standings, has been tipped as a likely candidate to replace Hayden at the Italian manufacturer although their bike is less competitive. (Reporting by Alan Baldwin in London, editing by Ken Ferris)