Peabody Energy Corp., the largest U.S. coal miner, said it might not be financially strong enough to remain in business in its current form and that the company might seek bankruptcy protection.

Peabody's ability to operate as a "going concern" is in doubt, the company said in a regulatory filing with the Securities and Exchange Commission Wednesday. "Going concern" is an accounting term used to describe a business that has the resources it needs to continue running.

St. Louis-based Peabody, which has been ravaged by the coal market's worst downturn in decades, has been seeking ways to ease its debt burden as rivals including Alpha Natural Resources and Arch Coal filed for bankruptcy. The company in recent months has struggled to close the sale of three coal mines in the western United States to Bowie Resource Partners and to renegotiate payment terms with its creditors.

"There can be no assurance that our plan to improve our operating performance and financial position will be successful," Peabody said in the 10-K filing. "We may need to voluntarily seek protection under Chapter 11."

The company elected to skip the semiannual coupons due Tuesday on $1 billion of 10 percent second lien notes maturing in March 2022 and $650 million of 6.5 percent unsecured bonds coming due in September 2020, according to the filing. It has a 30-day grace period to make the payment.

Peabody had warned in a previous filing that it might have to include the "going concern" language in the 10-K, but said that it could seek a waiver from lenders to avoid defaulting on a credit agreement. The company said Wednesday that its consolidated earnings before interest, taxes, depreciation and amortization will probably fall too low to comply with its financial covenants as of March 31.

"Absent waivers or cures, non-compliance with such covenants would constitute a default under the 2013 Credit Facility," the company said.