Banks’ main worry over the past two years has been the toxic assets on their balance sheets — other people’s debt.

Now they have to worry about their own.

About $10 trillion of bank debt comes due by the end of 2015, including $7 trillion by 2012, according to Moody's Investors Service.

Many banks will have to refinance that debt at much higher interest rates than were originally charged on it.

That’s because banks were able to borrow very cheaply during the credit bubble of 2003 to 2007.

Government guarantees for bank debt during the financial crisis allowed banks to issue debt at low rates, but it was short-term debt, which will soon become due.

The average maturity of new debt rated by Moody's dropped almost 60 percent since 2004 to 3.2 years.

It’s not just a U.S. problem. The average maturity for new bank debt worldwide fell almost 50 percent to 4.7 years during that period.

"We thought that we should send a (warning) signal" Jean-Francois Tremblay, a Moody's analyst, told The Wall Street Journal, referring to a report the firm recently issued about the problem.

A variety of experts say that despite the stabilization of the financial system over the last eight months, banks still face tremendous problems.

Chris Whalen, managing director of Institutional Risk Analytics, told Bloomberg 1,000 banks may ultimately fail.

His firm currently gives 2,200 banks an “F” grade and believes about half that total need to be restructured.