(Reuters) - Samsung Electronics Co Ltd (005930.KS) plans to launch the first smartphone based on its Tizen operating system in the third quarter, marking the company's latest bid to build up its own ecosystem and reduce reliance on Google Inc's (GOOGL.O) Android.

The South Korean firm on Monday said the Samsung Z, which comes with a 4.8 inch high-definition display and offers features such as a fingerprint sensor, will be unveiled at the Tizen Developer Conference in San Francisco on Tuesday.

The phone will be available in Russia sometime in the July-September period with other markets to follow, the firm said in a statement without specifying which markets.

Samsung did not offer sales forecasts or how much the phone will sell for, though an executive told Reuters in April that the company is working on at least two models powered by Tizen and that will be released "in a few countries where we can do well."

The Samsung Z would be the latest effort by the electronics giant to build momentum for Tizen, with its Gear 2 smartwatches also powered by the platform.

The majority of Samsung's mobile devices are based on Google's Android platform. The push to develop its own operating system is part of efforts to reduce dependence on the U.S. firm, but delays in product launches have undercut expectations.

The Samsung executive said in April he thinks Tizen would have to account for up to 15 percent of Samsung's total smartphone shipments to be deemed a success.

"There is plenty of room and plenty of opportunity for a strong third vendor; arguably if you can carve out 10 percent of a two billion units market in smartphones (by 2018), then that could be an opportunity," said Rachel Lashford, Singapore-based analyst at Canalys.

Many in the industry are still in the dark about Tizen, however, so there are questions about Samsung's level of commitment to the platform, Lashford said.

Analysts also say it will be difficult for Samsung to lure enough developers to make the apps and services necessary to mount a serious challenge to dominant platforms Android and iOS from Apple Inc (AAPL.O).

Samsung declined to say how many apps are available for the operating system.

"The market for Tizen won't be as big as Android or Apple's iOS, so I think it will be a challenge for Samsung to build up an ecosystem," said IM Investment analyst Lee Min-hee.

Tizen may be more useful as leverage in future negotiations with Google, Lee said.

(Reporting by Se Young Lee; Editing by Christopher Cushing)