Sears Holdings announced Thursday that it had lost nearly $1 billion in the first six months of the year.

The company has been bleeding money for several quarters as its leadership tries to transform the business from a traditional retailer into a more targeted company that relies on loyal shoppers, who are offered personalized deals.

Members of its free Shop Your Way rewards program accounted for 73 percent of quarterly sales, the company said Thursday, and its online sales in the quarter grew 18 percent from the period a year earlier.

Nonetheless, rewards for the company have not materialized. Sears Holdings, which owns Sears and Kmart stores, lost $573 million in its second quarter and $975  million during the first half of the year. The company’s quarterly revenue declined to $8.01 billion, from $8.87 billion in the period a year earlier.

The company’s chief executive, Edward S. Lampert, a hedge-fund magnate whose investment acumen was once compared to that of Warren E. Buffett, called the performance unacceptable and sought to assure investors that he was committed to reversing the retailer’s fortunes.

“As the CEO and the largest individual shareholder of Sears Holdings, I am personally committed to driving our transformation, improving the profit performance of the company and creating shareholder value,” Lampert said in a statement.

Last week, Wal-Mart cut its full-year earnings guidance, and a few days later, Target reported a disappointing quarter. The results from Sears, however, have easily been among the worst.

Also reflected in the quarterly earnings Thursday was the separation of Lands’ End from the business.