Google's Android is the most popular smartphone operating system in the United States -- but just barely, according to new numbers from the Nielsen Company. The metrics firm found that Android has captured 29 per cent of the hearts and minds of U.S. smartphone users, while Research In Motion's Blackberry and Apple's iPhone trail at 27 per cent each. The findings are a marked difference from a Nielsen report released in December that found the iPhone had about a four per cent lead on its Google rival. The December study also said Android and iPhone devices were equally desirable among U.S. users.