Indianapolis Motor Speedway, which holds a contract to host MotoGP until 2014, could withdraw from the calendar after this year's event.

Mark Miles, CEO of circuit owners Hulman & Co., told the Indianapolis Star that IMS has a brief window after this year's event to opt out.

"Our mindset now is that we're going to go through 2014, but we're going to look at this year and evaluate [the MotoGP event] right after."

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The doubt for Miles is reported to be the 'inability to draw a large crowd' for MotoGP, although he puts 'significant onus on his team for being too focused on the Indianapolis 500 and IndyCar'.

The Indianapolis MotoGP round has long been rumoured as under threat.

Last month, Dorna CEO Carmelo Ezpeleta was quoted as saying: "I don't think we will continue with three [races in America]" with Indianapolis reported as the likely venue to be dropped.

Indianapolis joined the MotoGP calendar in 2008, using a modified version of the previous F1 circuit. California's Laguna Seca was the first US-based event of the four-stroke MotoGP era, arriving in 2005, with Austin, Texas making its debut earlier this year.