The financial crisis that began 13 months ago has entered a new, far more serious phase.

Lingering hopes that the damage could be contained to a handful of financial institutions that made bad bets on mortgages have evaporated. New fault lines are emerging beyond the original problem — troubled subprime mortgages — in areas like credit-default swaps, the credit insurance contracts sold by American International Group Inc. and others. There's also a growing sense of wariness about the health of trading partners.

The consequences for companies and chief executives who tarry — hoping for better times in which to raise capital, sell assets or acknowledge losses — are now clear and brutal, as falling share prices and fearful lenders send troubled companies into ever-deeper holes. This weekend, such a realization led John Thain to sell the century-old Merrill Lynch & Co. to Bank of America Corp. Each episode seems to bring government intervention that is more extensive and expensive than the previous one, and carries greater risk of unintended consequences.

Expectations for a quick end to the crisis are fading fast. "I think it's going to last a lot longer than perhaps we would have anticipated," Anne Mulcahy, chief executive of Xerox Corp., said Wednesday.

"This has been the worst financial crisis since the Great Depression. There is no question about it," said Mark Gertler, a New York University economist who worked with fellow academic Ben Bernanke, now the Federal Reserve chairman, to explain how financial turmoil can infect the overall economy. "But at the same time we have the policy mechanisms in place fighting it, which is something we didn't have during the Great Depression."

The U.S. financial system resembles a patient in intensive care. The body is trying to fight off a disease that is spreading, and as it does so, the body convulses, settles for a time and then convulses again. The illness seems to be overwhelming the self-healing tendencies of markets. The doctors in charge are resorting to ever-more invasive treatment, and are now experimenting with remedies that have never before been applied. Fed Chairman Bernanke and Treasury Secretary Henry Paulson, walking into a hastily arranged meeting with congressional leaders Tuesday night to brief them on the government's unprecedented rescue of AIG, looked like exhausted surgeons delivering grim news to the family.

Fed and Treasury officials have identified the disease. It's called deleveraging, or the unwinding of debt. During the credit boom, financial institutions and American households took on too much debt. Between 2002 and 2006, household borrowing grew at an average annual rate of 11%, far outpacing overall economic growth. Borrowing by financial institutions grew by a 10% annualized rate. Now many of those borrowers can't pay back the loans, a problem that is exacerbated by the collapse in housing prices. They need to reduce their dependence on borrowed money, a painful and drawn-out process that can choke off credit and economic growth.

At least three things need to happen to bring the deleveraging process to an end, and they're hard to do at once. Financial institutions and others need to fess up to their mistakes by selling or writing down the value of distressed assets they bought with borrowed money. They need to pay off debt. Finally, they need to rebuild their capital cushions, which have been eroded by losses on those distressed assets.

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