U.S. new-vehicle sales are set to rise in September from a year ago, helped by sustained demand, according to Cox Automotive.

Sales volumes in the current month are set to touch nearly 1.3 million units, up more than 13% from a year ago, according to the auto research firm.

Despite rising interest rates on new vehicle loans and a strike by the United Auto Workers (UAW) union against major U.S. automakers, industry-wide inventory levels are up more than 63%, the report said.

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The ongoing labor strike between the UAW and automakers Ford, General Motors and Chrysler parent Stellantis, targeting some U.S. facilities at each company, has threatened the supply of newer models.

"Pent-up demand has been fueling the vehicle market this year. Consumers, and even more so large fleets, have become buyers as inventory improves," said Charlie Chesbrough, Cox Automotive senior economist.

The auto research firm also raised full-year new-vehicle sales forecast to between 15.3 million and 15.4 million units, from 15 million units.