Motorola took a 50 percent stake in UIQ, a move that is likely a reaction to stepped up competition from the iPhone.

Under the agreement, Motorola and Sony Ericsson Mobile Communications will equally share ownership of UI Holdings, the parent company of Symbian user interface developer UIQ Technology.

Motorola's interest in UIQ could be an effort for the handset maker to produce more user friendly devices in the face of competition from Nokia and Apple, said Gerry Purdy, chief analyst at Frost and Sullivan. UIQ was developed early on as a touch-based user interface. That concept has seen renewed interest since the launch of Apple's iPhone, which has a unique touch screen user interface.

The investment in UIQ could signal that Motorola plans to release more Symbian phones, Purdy said. The announcement could also mean that Motorola hopes to influence the development of UIQ such that the software could become compatible with other operating systems like Linux, he said.

Motorola is better known for its Linux phones than its Symbian handsets. In fact, in 2003 Motorola sold its stake in Symbian, a decision that many in the industry interpreted as a move away from the operating system.

Sony Ericsson and Motorola are inviting other handset makers to either become shareholders of UIQ or license the technology. Historically, UIQ has been used almost exclusively by Sony Ericsson and Motorola.

UIQ competes with Nokia's Series 60 software, a user interface that also runs on Symbian. Both efforts have faced difficulties in enticing other phone makers to license the software because of the conflict of ownership. For instance, some phone makers may be reluctant to license Series 60 software from their competitor, Nokia.

UIQ has its roots in an Ericsson development lab founded in 1998. The lab soon became a part of Symbian and earlier this year Sony Ericsson acquired the company from Symbian.