Google is to release a mobile phone platform in mid-2008 rather than a widely predicted mobile handset, according to The Wall Street Journal.

The mobile phone platform will appear in mid-2008 and will incorporate a variety of Google online services, also allowing outside developers to create applications. The goal is to make Google applications and services as easily accessible on mobile phones as PCs, so that the company can extend its advertising business to mobile phones and other wireless devices.

Google may announce its mobile platform within weeks, according to the Journal.

The Journal's article, based on anonymous sources, is the latest of multiple reports over the past six months or so about Google's plans for the mobile market.

Although at some point it was speculated that Google might be involved in the actual manufacturing of phone hardware, that rumour is now discredited, as Google is expected to focus on developing mobile software.

For Google, it is critical to replicate on mobile phones the success it has had on PC-based online advertising. After years of unfulfilled promises, mobile advertising will boom in coming years, as people spend more time using the Internet via their mobile phones.

Worldwide, mobile ad spending is expected to reach $1.5bn this year and grow to $11.3bn by 2011, according to market researcher Informa Telecoms & Media.

Google is far from alone in its interest at pursuing this emerging opportunity in the mobile market, where all major telecom, online publishing and Internet players are jockeying for position.

Of course, delivering online services and applications via mobile phones isn't as straightforward as doing it via PCs. In the mobile market, providers of online applications often have to strike up deals and partnerships with handset makers and wireless carriers.

In a recent interview, Marissa Mayer, Google's vice president of Search Products & User Experience, acknowledged there are specific challenges to bringing Google services to mobile-phone subscribers.

"The mobile space is very complicated," she said.

Google has pursued various avenues for making its search engines and other services available via cell phones. It has adapted Google websites for mobile browsers, developed mobile applications people can download themselves, as well as preloaded Google software in handsets via formal partnerships with mobile industry players.