Aiming for one billion Twitterers by 2013?

Twitter’s International Team Lead Engineer Matt Sanford has blogged on the company’s site that Twitter is seeing growth of over 60 percent in registrations outside the U.S.

After setting up a Spanish language capability in November, the microblogging service saw a huge surge in registrations in Latin America, Sanford said. Sign-ups in India also spiked early in the year after several politicians and Bollywood movie stars began Tweeting.

The service was thought to have 75 million users at the end of January (“New Data on Twitter’s Users and Engagement” ) and documents obtained from Twitter by a hacker and published in 2009 showed that the company had plans to sign up one billion users by the end of 2013.

Several sources have estimated that at the end of 2009 1.7 billion people ere using the Internet.

Twitter Blog: “Growing around the world”