Sina's Chinese-language Weibo product was launched about two years ago and claims more than 140 million users.

Technology blog TechWeb reported on Monday that Sina was going to launch an English microblog in the United States in a few months to rival Twitter.

Access to Twitter from within China is blocked by the Chinese government.

Sina's spokesman Liu Qi said an English microblog was in the works but its release was not catered to a particular market.

"We won't be launching it in one particular market, the idea is to have the English version to cater to our many overseas users," Liu told Reuters, adding that more than 10 percent of Weibo's users are based overseas.

The English version will launch by the end of the year and will be subject to Chinese regulations, Liu said.

China fears that unfettered access to the Internet would spark instability that could undermine Communist Party rule. Besides Twitter, China also blocks Facebook and YouTube because the government is unable to monitor and censor content on those websites.

Many Chinese companies offering similar social-networking services such as Renren Inc's Renren Wang and Kaixin001 have sprung up. These Chinese sites actively police content and censor material that could be deemed politically sensitive.