NEW YORK (CNNMoney) -- 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.

The company issued a statement later Wednesday stressing that despite the cautionary language in the annual report, it believes it is on course to turn around its struggling business.

"It is very important to reiterate that Sears Holdings remains focused on executing our transformation plan," said Chief Financial Officer Jason Hollar. "This is evident in the decisive actions we have taken in recent months. Despite the risks outlined we remain confident in our financial position."

Still, Sears Holdings has been in trouble almost since the 2005 merger that joined the two department store brands.

At the start of 2006, it had 3,400 U.S. stores and 370 more in Canada that it has since sold. By the end of this January, it had only 1,400 stores left, all in the United States. The company still has 140,000 employees, but that too is down sharply from the 355,000 it had in 2006.

For more information go to http://www.CNN.com