After years of huge losses and store closings, the future is officially in doubt for Sears and Kmart. Sears Holdings, the holding company for the two iconic retail brands, warned investors late Tuesday that it can’t promise it will stay in business. It included the language in its annual report while insisting it might still turn things around. “Our historical operating results indicate substantial doubt exists related to the company’s ability to continue as a going concern,” said the statement. While its recent history has been written in red ink, Sears was once one of the nation’s most powerful companies, both the Walmart and Amazon of its time. But its once-proud brands have mostly been forgotten by the modern American shopper. Now Sears Holdings is not even sure it can raise enough cash through loans and debt financing to survive. The company owes $4.2 billion, up from about $3 billion a year ago. It lost $2.2 billion in the fiscal year ending in January and has not turned an annual profit since 2010. Its losses since then total $10.4 billion. Sears Holdings said its ability to sell assets, such as stores and store leases, could be limited because it needs those assets to pay for pension plans. In January, Sears sold its Craftsman brand of tools to Stanley Black & Decker. It is looking to sell Kenmore appliances and Diehard auto parts.