Shares of Sina were up about 4 percent in high-volume trading on Monday.
Sina, which has seen its stock soar on investor hopes that Weibo will be monetized sooner rather than later, reported in May, a 39 percent decline in quarterly net profit after it invested heavily in the platform.
Sina hopes to have more than 200 million Weibo users by the end of the year, up from 140 million currently.
The planned launch would mean direct competition with popular U.S. microblogging service Twitter, the blog said.
Sina's shares were trading at $115.49, following the news on Monday, on Nasdaq.