Microsoft launched a redesigned MSN portal optimized for mobile phones on Sunday.

U.S. mobile Internet use still represents only a fraction of computer-based Web usage, but technology heavyweights like Microsoft see increasingly powerful mobile phones and faster networks opening the door for new services and content.

Microsoft's new MSN Mobile portal -- http://mobile.msn.com -- offers news, sports information, entertainment features and access to services like e-mail, search, maps and instant messaging all on one page.

When a user accesses the portal, the MSN platform detects the handset and optimizes the site for that device, adjusting things like font sizes for different screens.

Microsoft's Web competitors Google and Yahoo are also trying to establish a mobile Internet presence while wireless carriers want to keep their consumers close with portals of their own.

The ultimate prize for all the players is to gain a foothold in the market for mobile advertising. Microsoft said it will not place advertising on the portal right away, but said it expects to have either banner, text or click-to-call ads in place this year.

The launch of the new MSN Mobile portal comes a few weeks before Apple releases its highly anticipated iPhone, which features a Safari browser that allows users to view full Web pages by zooming in and out.