In a sign that it's not prepared to bet its mobile business on its unproven Silverlight Web presentation technology, Microsoft has agreed to license rival Adobe's Flash Lite graphics software for use on cell phones, PDAs, and other portable devices powered by the Windows Mobile operating system.

Microsoft has also licensed Adobe Reader LE software for use with Windows Mobile, Adobe said Monday. Reader LE will allow Windows Mobile users to open and view documents and e-mails stored in Adobe's Portable Document Format.

"Bringing Flash Lite and Reader LE to the Windows Mobile experience will give consumers more of their favorite Web sites on the go," said John O'Rourke, general manager for Microsoft's Mobile Communications business unit, in a statement.

Under its agreement with Adobe, Microsoft will make versions 3 or higher of Flash Lite available as a plug-in for the Windows Mobile OS. "We're thrilled to work with Microsoft," said Adobe senior VP Al Ramadan.

Operating systems -- mobile or desktop -- require a graphics plug-in to correctly render the rich media and animations offered up by today's Web sites. Adobe Flash has long been the standard for such plug-ins, but Microsoft recently introduced its Silverlight technology as an alternative.

Microsoft's problem is that a version of Silverlight for portable devices isn't yet ready. Silverlight 1.0 for Windows Mobile 6 won't be available until the second quarter, Microsoft has said.

Microsoft's concern: If Windows Mobile doesn't support the latest display technologies, then device makers could opt for rival platforms such as Google's nascent Android OS.

There's also the fact that Silverlight remains relatively unproven, and the vast majority of Web developers continue to design pages with Flash in mind. More than 500 million mobile devices already carry Flash Lite, according to Adobe.

In addition to Windows Mobile, Flash Lite is compatible with Symbian's S60 OS and Qualcomm's BREW platform.