NEW YORK (Reuters) - Citigroup Inc. could take substantial write-downs for sub-prime mortgages, leveraged buyout loans and other assets in the second quarter, the company's chief financial officer said on a call with investors yesterday.

In at least some of these areas, the write-downs are on track to be smaller than the first quarter, but could still be substantial, chief financial officer Gary Crittenden said.

Mr. Crittenden's disclosure, in a conference call sponsored by Deutsche Bank, sent Citi shares four percent lower, while rival banks Bank of America Corp. and JPMorgan Chase & Co. were down 4.4 percent and 3.3 percent, respectively.

Also in reaction to Mr. Crittenden's comments, Citi's debt protection costs rose.

Mr. Crittenden also said the bank could face another credit value adjustment similar to the last quarter from exposure to bond insurers. In the first quarter, in which Citi posted a $5 billion loss, the bank took a $1.5 billion write-down for exposure to bond insurers.

Costs linked to worsening consumer credit quality could have a meaningful impact on Citi's results for the rest of the year, Mr. Crittenden said.

The company is always willing to look at acquisitions, and will make them where it makes sense, but is focusing more on improving its performance, he said.