Recent actions by a high-profile ratings agency could put lenders on the hook for a $7 billion credit to Xerox Corp. Moody's Investors Service sparked concern among Xerox's lenders Friday when it downgraded the company's long-term senior unsecured credit rating to Ba1 from Baa2 and its short-term rating to "not prime" from "prime 2. " Moody's cited illiquidity, an inefficient cost structure, increased competition, decreased demand, and three restructurings since 1998 as reasons for the downgrading. Most importantly from a lender's perspective, the move called into question a $7 billion loan backed by 58 banks. The credit, which was arranged in October 1997, was led by Bank One Corp., Citigroup Inc., Chase Manhattan Corp., and J.P. Morgan & Co., each of which lent Xerox $375 million. The current quarter has been filled with corporate bankruptcies and big losses on loans to such troubled companies as Sunbeam Corp.