Nokia said on Tuesday that it made a cash offer of $411 million for the 52 percent stake in the assets of mobile operating system seller Symbian that it does not already own.

If it succeeds in acquiring Symbian, Nokia said it will contribute the operating system's code to the Symbian Foundation, an organization announced on Tuesday, and make the code available to Foundation members for free.

The Foundation, which will include founding members AT&T, LG Electronics, Motorola, NTT DoCoMo, Samsung, Sony Ericsson, STMicroelectronics, Texas Instruments, and Vodafone, will also offer S60, UIQ, and MOAP assets for free. 

The move is seen as a dramatic response to mobile market inroads made by Google's Android, Linux, and the iPhone.

Linux has made significant progress as a mobile operating system and the iPhone has changed users' expectations, but the biggest threat to Nokia, experts say, is Google's presence in the mobile operating system market.

"With Google's Android as a force on the horizon, Nokia had to do something and making Symbian available to other developers for free is a good move under the circumstances," said Moe Tanabian, a principal with IBB Consulting. 

Google unveiled Android, its open-source mobile operating system, last November along with the 34-member Open Handset Alliance, which included many of the industry's major players. All of the mobile handset leaders, except for Nokia, are members of the Google-led alliance. (see Google Opens Mobile Plans)

"There has been financial pressure on Nokia to move in this direction at some point," said Stuart Carlaw, an analyst with ABI Research. "The sheer economics of the number of devices it ships with the OS versus the value it gets out of its historic shareholding clearly indicated that such a 'rescue' was inevitable at some point."

More than 200 million Symbian-based phones have been shipped on more than 250 mobile networks around the world.

Much of the focus of the mobile industry is moving inexorably away from the operating system and toward services such as location-based search, navigation, social networks, mobile ads, and maps, Mr. Tanabian said.

"Nokia is keenly aware of that so it has been investing in mobile services because those services will be the major mobile revenue generators going forward," he said.