Rihanna has been forced to scrap another date on her U.S. tour due to poor ticket sales.

The Umbrella hit-maker axed the launch show of her Last Girl On Earth Tour with Ke$ha last week. Her tour promoters blamed changes in production for the cancellation.

However, the jaunt has been hit hard again - her show at Indiana's Verizon Wireless Music Center on August 3rd has been called off, according to ticketing websites. It is believed poor sales figures have forced the move.

The cancellation follows news that America's concert revenues are down in 2010 following a stellar 2009, with the Jonas Brothers and the stars of American Idol also scaling down their upcoming tours.

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