CALABASAS, California (AP) -- Countrywide Financial Corp., the U.S.'s largest mortgage lender, said Thursday it had to draw on an $11.5 billion (euro8.53 billion) credit line amid a crisis in liquidity.

Countrywide also said it will accelerate its plans to migrate its mortgage production operations into its banking operations.

The secondary market for mortgages has all but disappeared in recent weeks as investors have worried about the value of loans and rising delinquencies and defaults.

Mortgage lenders rely on the secondary markets to borrow money to make more loans. The problems started as subprime mortgages -- loans given to customers with poor credit history -- started going delinquent and defaulting at faster rates.

The problems have spread to the broader mortgage market, making investors nervous about nearly all types of loans that cannot be purchased by Fannie Mae or Freddie Mac.

Such "conforming" loans are considered safer because Fannie and Freddie are government-sponsored entities. Countrywide said some 90 percent of the loans it originates from now on will be conforming loans or will meet its internal bank criteria.

Shares of Countrywide fell $1.29, or 6.1 percent, to $20 in premarket trading. Shares have traded between $19.25 and $45.26 during the past year.