Apple's iPhone remained the most popular smartphone among US buyers in the closing months of 2012 while Android handsets were on top worldwide, Kantar Worldpanel ComTech reported on Tuesday. "At the end of 2012, the global (operating system) picture shows Android on top, but clearly the rate of growth it experienced over the past year is beginning to slow as easy wins from first-time smartphone buyers begin to reduce," said Kantar global consumer insight director Dominic Sunnebo. Apple iPhones accounted for 51.2 percent of smartphone sales in the United States during the 12-week period ending December 23rd of last year, according to Kantar. Smartphones powered by Google-backed Android software made up slightly more than 44 percent of sales while handsets based on Microsoft's Windows operating system were a distant third-place with 2.6 percent, the report indicated. Android smartphones continued to be best sellers in major markets including Britain, China, Spain, Australia, and Germany while iPhones were favored in Japan as well as the United States, according to Kantor. Windows smartphones appeared to be catching on in Europe, with its shares of sales in Britain and Italy climbing to 5.9 and 13.9 percent respectively, the reported indicated. "Windows Phone is now starting to gain respectable shares in a number of key European countries," Sunnebo said. "However, its performance in the Chinese and US markets remains underwhelming; these remain key challenges for Microsoft to overcome during 2013."