Although Google has declined to comment for months on its rumored move into the mobile space, sources said the company will make an announcement Monday at 11 a.m. ET, and that details of the plan are being finalized this weekend.

Google will announce an open source development platform for mobile applications that will contain a full set of components, including an operating system, a set of common APIs, a middleware layer, a customizable user interface and even a mobile browser, sources said. Instant messaging standard protocols will also be supported.

The platform is intended to simplify the process of creating and deploying mobile applications, so that an application can be built once and be compatible with multiple phones.

On the partner side, well over 30 industry heavyweights are already on board, including Intel, Qualcomm, Broadcom, Nvidia, Sprint Nextel, T-Mobile, China Mobile, Telefonica, NTT DoCoMo, LG Electronics and HTC, the sources said.

With negotiations expected to continue through the weekend and into Monday morning, it's possible that the list could exceed 40 partners. Among those not supporting the announcement at press time are Nokia, Verizon and Apple.

The development platform will be freely available to anyone who wants to use it, and, aside from a common core, will provide a lot of flexibility for modifications and extensions.

The ultimate goal is to lower the costs and simplify the creation of mobile applications and spur innovation that, as Google sees it, has been hampered by technical fragmentation. As such, the Google offering will rival existing mobile platforms from Microsoft and Symbian.

For Google, the benefit will come indirectly from an acceleration in improvements to mobile phone interfaces, which the company reasons will make it easier for people to access online services, like search engines, and applications, from their mobile phones. The intent is to bridge the gap between the Internet and mobile phones.

As usage of Google online services increases on mobile devices, so will the advertising revenue the company generates.

Mobile advertising is a tiny market but is expected to grow quickly in coming years. According to Opus Research, mobile advertising spending in North America and Western Europe will reach a combined US$5.08 billion by 2012, up from an estimated $106.8 million at the end of this year. This represents a compound annual growth rate (CAGR) of 116 percent.