By Walden Siew

NEW YORK (Reuters) - Wall Street banks are facing a "systemic margin call" that may deplete banks of $325 billion of capital due to deteriorating subprime U.S. mortgages, JPMorgan Chase & Co (JPM.N: Quote, Profile, Research), said in a report late on Friday.

JPMorgan, which sent a default notice to Thornburg Mortgage Inc. (TMA.N: Quote, Profile, Research) after the lender missed a $28 million margin call, said more default notices and margin calls were likely. The Carlyle Group's mortgage fund also failed to meet $37 million in margin calls this week.

"A systemic credit crunch is underway, driven primarily by bank writedowns for subprime mortgages," according to the report co-authored by analyst Christopher Flanagan. "We would characterize this situation as a systemic margin call."

The credit crisis that began about a year ago will likely intensify after Friday's weak February U.S. employment report "that most definitely signals recession," JPMorgan said.

Indeed, corporate bond spreads widened to a new record on Friday, surpassing levels seen in October 2002 during a boom in bankruptcies following the dot-com crash. U.S. employers cut payrolls in February for a second consecutive month, slashing 63,000 jobs, the biggest monthly job decline in nearly five years, the U.S. Labor Department reported on Friday.

"The weak February employment report points to an economy in recession," JPMorgan said.

The JPMorgan report included a revised bleaker forecast for subprime-related home prices. The bank now sees prices falling 30 percent, from its prior 25 percent forecast. Those prices have declined 14 percent since mid-2006, JPMorgan said.