Toyota Motor Corp. is making rare styling changes in the Camry sedan just halfway into the car's usual design cycle, a sign the automaker is eager to stem gains made by Hyundai Motor Co.'s Sonata, which also is being reworked for 2015.

The latest Camry and Sonata models were to make an appearance at the New York International Auto Show on Wednesday, when it opens to the press, before joining the midsize sedan market fray. Toyota, the world's largest carmaker, is looking to extend the Camry's 12-year run as the top-selling U.S. car, while Hyundai is confident enough to tone down the curving lines from the breakthrough version of the Sonata that reached the U.S. in 2010.

"If you think of it in terms of traditional leader and traditional challenger actions, their positions are switched," Eric Noble, president of industry consultant CarLab, said in an interview. "What we've had the last two years is Toyota being put in the challenger position, trying to regain ground, in no small part because of Hyundai."