* Twitter-like Sina Weibo could be worth at least $4.3 bln
* IPO comes as Chinese companies flock to U.S. markets
By Elzio Barreto and Paul Carsten
HONG KONG/BEIJING, Feb 24 (Reuters) - Sina Corp has hired Credit Suisse AG and Goldman Sachs Group Inc for a U.S. initial public offering worth about $500 million of its Sina Weibo microblogging service, a source familiar with the plans said on Monday.
Sina Weibo, one of several Chinese Twitter-like short messaging blogs, plans a listing in the second quarter, added the source, who was not authorized to speak publicly on the matter. The IPO plans were initially reported by the Financial Times.
The IPO follows Facebook Inc's $19 billion purchase last week of fast-growing mobile-messaging startup WhatsApp and a surge in Internet-related equity deals and mergers and acquisitions.
Sina Weibo's offering would also come as Chinese companies flock to the U.S. IPO market in their biggest numbers since 2010 because of soaring valuations.
Sina will announce its fourth-quarter earnings after markets close in New York on Monday. The company declined to comment on the listing plans when contacted by Reuters.
Alibaba Group Holding Ltd bought an 18 percent stake in Sina Weibo for $586 million last April, valuing Weibo at $3.3 billion. Since then Sina's stock price has risen by one-third, implying the microblogging business could now be worth at least $4.3 billion. Alibaba also declined to comment.
As part of its initial deal with Weibo, Alibaba has an option to increase its stake in Sina Weibo to 30 percent for an unspecified amount within a certain time period, although it is unclear whether this has passed.
Microblogging may be on the decline in China however, as users opt for more private mobile messaging apps over public platforms like Sina Weibo.
Blockbuster mobile messaging apps like Tencent Holdings Ltd's WeChat, or Weixin in China, have become venues of choice for users who want to express views without fear of retribution. The government last year started clamping down on "online rumours" which it says threaten social stability.
The number of microblog users fell 9 percent last year as people jumped to mobile messaging apps like WeChat, according to a January report from the official China Internet Network Information Center which sent Sina tumbling.
Despite the decline in microblog users, Sina has been able to wring money from its service. Weibo advertising revenues for the quarter ending September 2013 grew 125 percent year-on-year to $43.7 million, according to Sina. Non-advertising revenues from Weibo's value-added services, such as Weibo membership fees and games, more than doubled, rising 121 percent year on year to $9.7 million.