NEW YORK: A new, cheaper version of Amazon's popular Kindle e-reader will feature on-screen ads, the online retailer has said.

The device, Kindle With Special Offers, which will retail for $114 (€79, £70), is now on sale for pre-orders in the US and will ship in early May.

An ad-free version of the same device is currently available for $139.

Marketing messages will appear to users in the form of "sponsored screensavers", meaning that they will only appear when the device is unused for a certain length of time.

Advertisers signed up to appear on Kindle With Special Offers include General Motors and Procter & Gamble.

The launch of the device will also be supported by a range of discount deals for buyers, including a $1-per-album deal for Amazon's mp3 store and $10 for a $20 Amazon gift card.

Jeff Bezos, Amazon ceo, said: "We're working hard to make sure that anyone who wants a Kindle can afford one."

Speaking to Bloomberg, Jay Marine, director of Kindle products, said: "Every time we've been able to make Kindle more affordable, we've seen huge growth in demand."

Amazon's Kindle, launched in 2007, is the world's most popular e-book reader, with global sales thought to have reached 8m in 2010, according to a Bloomberg poll.

IMS Research figures also suggest that Amazon's global share of the e-reader category rose by 14 percentage points to 59% over the course of last year.

Data sourced from Amazon/Bloomberg; additional content by Warc staff