The bankruptcies of both General Motors Corp. (GMGMQ) and Chrysler LLC will cost five steel companies a combined $68.78 million if the auto makers fail to pay their bills, according to court filings from the two auto makers.

GM and Chrysler, the largest and third-largest carmakers in the U.S., may owe even more money to steelmakers depending on whether other steel producers filed claims that weren't disclosed among the list of top 50 creditors in each of their bankruptcy filings. Similarly, the figure may be lower in Chrysler's case as it started to emerge from bankruptcy this week.

GM filed for Chapter 11 bankruptcy proceedings on Monday, making it the second-largest company to do so in U.S. history. Chrysler filed the same bankruptcy proceeding a month ago and is this week finalizing plans to merge its assets with Italy's Fiat SpA (FIATY), a move that will help pave the way for the U.S. auto maker to emerge from bankruptcy.

The U.S. automotive industry is the second-largest steel consumer in the U.S. followed after construction. The U.S. automotive industry accounts for about 16% of total U.S. steel shipments.

The two cash-strapped carmakers have suffered from decades of cumbersome labor legacy costs and declining market share, but their liquidity issues became more acute when sales plummeted due to lack of consumer demand from the sudden economic downturn.

Steelmakers and component part suppliers have been among the hardest hit by the bankruptcies and took action months ago to conserve cash by slashing production, cutting jobs and shelving expansion projects. But now both face the prospect of unpaid bills.

In the steel industry, U.S. Steel Corp. (X), the U.S.'s second-largest steelmaker by volume after Nucor Corp. (NUE), has the largest exposure out of the steelmakers to the two bankruptcies.

GM and Chrysler owe U.S. Steel a combined $25.77 million - $16.2 million from Chrysler and $9.6 million from GM.

A U.S. Steel spokeswoman declined to comment, noting that "we don't comment publicly about our customers."

AK Steel Holding Corp. (AKS), the U.S.'s fifth-largest steelmaker by volume, has the second-largest exposure among steelmakers to the two auto makers: a combined $15.73 million.

AK Steel spokesman Alan H. McCoy said the company was confident it would be repaid and said it is willing to supply steel to both companies, although Chrysler has shut all of its automobile production until sometime in June and GM plans to shut down production for several weeks over the summer.

The U.S. units of ArcelorMittal (MT) and OAO Severstal (CHMF.RS), the country's third and fourth-largest steelmakers, are owed a combined $15.39 million and $6.69 million respectively, according to the bankruptcy proceedings.

ArcelorMittal and Russia's Severstal wouldn't comment on the bankruptcy proceedings but said they continue to value their relationship with both carmakers.

Steel processing company the Worthington Steel Co., a unit of Worthington Industries Inc. (WOR), was owed $5.20 million but only from Chrysler, the least amount out of the five steel companies. George Stowe, president of Worthington Industries, said Chrysler has already paid back all its bills and his company is prepared to do more business with Chrysler during the bankruptcy.

The steel companies are in a better position than other creditors who have larger exposures to the two bankruptcies.

The Wilmington Trust Corp. (WL), trustee for the bondholders, is GM's largest creditor with $22.76 billion in unpaid debt, followed by union workers with $20.56 billion in employee obligations.

In Chrysler's case, Ohio Module MFG Co. LLC is the largest creditor with $70.3 million in outstanding claims followed by advertising company BBDO Detroit Inc with $58.1 million in outstanding claims.

By comparison, U.S. Steel is the 13th and 31st-largest creditor in Chrysler and GM's respective bankruptcy filings even though it is considered the largest steel creditor in both cases.

The steel companies said they had already prepared themselves for the bankruptcy proceedings by idling production and had already taken steps to diversify their business over recent years in order to reduce their exposure to the ailing U.S. automotive industry.

-By Alex MacDonald, Dow Jones Newswires; 44 20 7842 9328; alex.macdonald@dowjones.com