(Corrects R.H. Donnelley's headquarters to Cary, North Carolina in second paragraph)

NEW YORK, Feb 9 (Reuters) - Moody's Investors Service on Monday warned that directory publishers R.H. Donnelley & Sons RHDC.PK and Idearc Inc IDAR.PK may be each likely to pursue a prepackaged bankruptcy or distressed debt exchange as they struggle to overcome high debt loads.

Moody's cut its R.H. Donnelley's corporate family rating to "Caa1," seven steps below investment grade and an extremely speculative rating, and cut the Cary, North Carolina-based company's probability of default rating to one step lower at "Caa2."

The corporate family rating of Idearc, the publisher of the Yellow Pages directories, was also cut two steps to "Caa2," eight levels below investment grade, and its probability of default rating was cut one step lower at "Caa3."

Both companies are suffering from a bigger drop in advertising revenues than was previously expected, Moody's said.

"Moody's had previously considered it likely that (R.H. Donnelley) would continue (but likely substantially expand) the scope of its recent debt repurchase activities to effect a reduced debt profile and improved credit metrics," Moody's said in a release.

However, "a pre-emptive restructuring now seems to be a more viable alternative given current market conditions, which are expected to facilitate a more expedient solution to alleviate the company's financial strain," Moody's said.

Prepackaged bankruptcies are filed when a company reaches an agreement with debtholders prior to filing for court protection.

Donnelley had $3.12 billion in long-term debt as of September 30, according to a regulatory filing.