China's Sina Corp will launch a virtual currency for its highly popular microblogging service, Weibo, in the third quarter this year, the firm's first real push to monetize the platform, said a source with direct knowledge of the matter on Wednesday.

Sina, which launched Weibo about two years ago, has more than 140 million users. In a document released online recently, Sina detailed the use of its virtual currency, Weibi, for developers. (http://open.weibo.com/wiki/index.php/)

Weibi is in the development stage now, but it will be launched very soon in the third quarter to a small portion of users before a full rollout later in the year, said the source, who declined to be named because the matter was not yet public.

One Weibi will have a value of 1 yuan and can be used to pay for virtual items and services.

The launch of the currency will be Sina's first major push to monetize the platform, which has attracted Western celebrities such as Tom Cruise, Bill Gates and Emma Watson.

Sina has said it is planning to launch an English version of Weibo as well as a version for businesses. The firm's chief executive Charles Chao said in April he had no plans to list Weibo in the near term and would diversify into casual game and e-commerce applications for the platform next year.

Sina competes with Tencent Holdings, China's largest Internet company, in the microblogging space. Tencent has over 160 million users on its microblog platform.

Sina's Weibo functions like Twitter, allowing users to post short messages, pictures and links to draw followers. Twitter, Facebook and YouTube are blocked in China as authorities fear unfettered access to the Internet would spark instability that could undermine Communist Party rule.

(Reporting by Melanie Lee; Editing by Jacqueline Wong and Jonathan Hopfner)

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