In the ongoing battle between digital book readers Sony Corp plans to introduce a line of upgraded digital book readers in the U.S. as early as next month to challenge Kindle-maker Amazon Inc, reports Bloomberg.

According to Phil Lubell, vice president of digital reading at Sony Electronics, the digital readers, which will be introduced in the U.S. in August, will be priced between $180 to $300 and come with hardware and software improvements.

According to Nobuo Kurahashi, an analyst at Mizuho Financial Group Inc., Sony appears to be struggling to expand its e-reader business as fast as it had originally planned.

Despite the fact that digital readers like Kindle and Barnes and Noble's Nook have an edge in the market, Sony plans to pursue it sale of digital readers. Sony plans to launch its new line of digital book readers in the U.S. before it introduces its first tablet-computer model as the former was cheaper, said Lubell.

Digital readers are more favored in the U.S. according to a recent survey. Bloomberg reports that Pew Research Center conducted a survey and found that the number of people who owned a digital reader had doubled to 12 percent in May from 6 percent in November while tablet owners had increased from 5 percent to 8 percent.

Compared to an iPad priced at $499 a digital reader like Kindle priced at $114 seems a more viable option.

We think there will still be a market for dedicated readers as long as tablets remain in the $500 price range, Lubell said.

According to Bloomberg, Apple's cheapest iPad is 67 percent more expensive than Sony's high end digital reader.

Lubell added that Sony plans to incorporate its online book store and e- book technology into its two tablet-computer models codenamed S1 and S2, which will be introduced in the U.S. later this year.