Sears is working to transform its business by selling brands like tool line Craftsman and building a stronger online presence. Its market share has been hurt by discount chains including Walmart (WMT.N), and the surge in popularity of online shopping has added to its woes. It was the second time in two years that Sears has expressed doubt about its business continuing as its losses mount. "This year's statement regarding its ability to remain a going concern is more dire," Ken Perkins, president of Retail Metrics Inc. "It has liquidated its best assets and the cupboard is bare. These losses are unsustainable." Sears declined to comment. Sales at Sears' established stores, including Kmart discount shops, fell 3.9 percent in its second quarter, compared with a drop of 11.9 percent in the first quarter, a positive sign sending the 125-year-old retailer's shares up 28 percent in extended trading.