Smartphone sales are expected to extend their strong growth trend in 2013 with some 918 million units worldwide, led by gains in big emerging markets China, Brazil and India, a survey showed Monday. The research firm IDC said 2013 will be the first year smartphones will outsell the more basic feature phones in the mobile market, and will account for 50.1 percent of all mobile phones. \"Smartphone prices have fallen globally, the smartphone strata are wider than ever, and the roll-out of data-centric fourth-generation wireless networks are three factors that have made these \'do-it-all\' devices an increasingly attractive option for users,\" IDC said. The research firm said that by the end of 2017, 1.5 billion smartphones will be shipped worldwide, over two-thirds of the total mobile phone market. IDC said the growing middle classes in China, Brazil, and India are driving up smartphone sales. China, which supplanted the United States last year as the global leader in smartphone shipments, is expected to see sales of 301 million this year, or 32.8 percent of the global market, ahead of the 137 million in the United States. \"While we don\'t expect China\'s smartphone growth to maintain the pace of a runaway train as it has over the last two years, there continue to be big drivers to keep the market growing as it leads the way to ever-lower smartphone prices and the country\'s transition to 4G networks is only just beginning,\" said IDC\'s Melissa Chau. India is expected to become the number three market for smartphones by 2017, and Brazil will be fourth, as those countries overtake mature markets like Japan and Britain, IDC said.