San Francisco - Microsoft said on Tuesday it would make its Surface tablet computer available to outside sellers as soon as mid-December, citing interest from retailers as well as consumers."The public reaction to Surface has been exciting to see. We've increased production and are expanding the ways in which customers can interact with, experience and purchase Surface," said Surface general manager Panos Panay, without providing any specific sales figures.A Microsoft statement said retail stores in the US and Australia would be the first to sell the introductory Surface model with Windows RT, which has many features of a tablet along with an attachable cover-keyboard.Retail availability in other countries will be announced in the coming months, said Microsoft, which began selling the Surface through its website, its "pop-up" holiday stores and permanent branded stores."Our plan has been to expand the retail presence for Surface after the first of the year," said Steve Schueler, head of retail sales for Microsoft."Based on interest from retailers, we are giving them the option to carry Surface with Windows RT even earlier."SalesAlthough Microsoft has provided no sales data, analysts have said Surface is getting only a small segment of the tablet market led by Apple's iPad, Amazon's Kindle and several others powered by the Google Android system.Microsoft also announced that some of its pop-up stores would remain open past the year-end holidays and several would become permanent Microsoft retail outlets."These stores will transition into either permanent brick-and-mortar retail outlets or specialty store locations," a company statement said.Surface, with a starting price of $499, is now sold at Microsoft retail stores in the US and Canada and online in the US, Australia, Britain Canada, China, France and Germany.Microsoft said in November that its Surface Pro, a version of its new tablet aimed at business users, would be available in January starting at $899 for US customers.