The two new models offer more capacity for the same price as today's models. The new 20GB iPod will sell for $299, while the top-of-the-line 40GB model will sell for $399. Apple had been selling a 15GB version for $299, a 20GB version for $399 and a 40GB model for $499.
The 15GB version, which had sold for $299, is no longer available.
The new iPods are available immediately at Apple retail stores, at its Web site and through resellers, the company said.
Apple trumpeted the news on its Web site Monday morning, but the details were first revealed Sunday as part of a Newsweek cover story on the iPod and its impact. The magazine's cover shows Apple CEO Steve Jobs holding one of the new, still-white models. In January 2002, a splashy new iMac was featured on the cover of Time.
The battery in the new iPods offers 12 hours of juice, up from an eight-hour rating for the current models. The jump comes from better power-management features, rather than a higher-capacity battery, according to Newsweek. The click-wheel interface is similar to the one Apple introduced in January with its iPod Mini.
There are also software advances, including the ability to listen to audio books at a faster or slower rate, as well as ways to create and edit more than one playlist from the iPod itself. Previously, only one playlist could be made and songs could be added, but not removed.
The iPod dock is included with the new 40GB model, but is a $39 add-on with the 20GB model. Neither includes a case.
The iPod has been a boon to Apple's sales and profits, with the company now selling roughly as many iPods as Mac computers.
The new models represent the fourth generation of the portable players. The first 5GB iPod debuted in October 2001, selling for $399 and featuring a mechanical wheel that spun to navigate through a library of songs. The iPod has kept its basic design since, though the wheel has become touch-sensitive, rather than mechanical, and the device has also slimmed down from its original size.
Meanwhile, competitors including Sony and Dell have introduced new hard-drive-based models, though none has yet to approach the iPod in terms of market share or as a cultural icon.
Hewlett-Packard, which had said it would start selling its blue, HP-branded iPod this summer, pushed out its launch to wait for the new model.
"We decided to wait for this amazing new fourth-generation iPod, as it will offer our customers an even better experience," CEO Carly Fiorina said in Apple's press release, adding that HP's iPod will be available in September.
Apple said that the company has no current plans for a 60GB iPod. Toshiba, which supplies the drives used in the iPod, said in June that a 60GB drive was in the works. A Toshiba executive was quoted in overseas press reports as saying Apple was a customer, though Toshiba executives in the United States would not comment.
The company also said Monday that the iPod's new software features, such as the enhanced on-the-go playlists and the improved audiobook handling, will not be made available for older iPods.
Separately, Apple said that Duke University will give Apple iPods to each of its 1,650 freshman this fall, allowing them to access class schedules and course information, as well as play music via the devices. A custom version of the iTunes site will allow students to both buy music and download class information. The school characterized the effort as a pilot program between Duke and Apple that will be evaluated after this year, adding that students will be able to keep their iPods either way.
"We're approaching this as an experiment, one we hope will motivate our faculty and students to think creatively about using digital audio content and a mobile computing environment to advance educational goals in the same way that iPods and similar devices have had such a big impact on music distribution," Tracy Futhey, Duke's vice president of information technology, said in a statement.
Apple has continued to lead the market for music players. In May 2004, iPod revenue accounted for 54 percent of MP3 music player sales through U.S. retailers, according to Ross Rubin, an analyst at NPD Group. NPD's figures do not include direct sales, such as those by Dell.
Rubin noted that Apple has remained competitive with many of the new entrants in the market. The company's products are not priced significantly higher than other, similar players--a key difference from the PC market, where Apple computers can cost hundreds of dollars more--and the iPod sports a number of design and software advantages.
Apple, however, will likely see competition in the mini players as new companies continue to join the market. "There are more hard drive suppliers," Rubin said.
CNET News.com's Michael Kanellos contributed to this report.