Regulators have told Bank of America Corp. and Citigroup Inc. that the banks may need to raise more capital based on early results of the government's so-called stress tests of lenders, according to people familiar with the situation.

The capital shortfall amounts to billions of dollars at Bank of America, based in Charlotte, N.C., people familiar with the bank said.

Executives at both banks are objecting to the preliminary findings, which emerged from the government's scrutiny of 19 large financial institutions. The two banks are planning to respond with detailed rebuttals, these people said, with Bank of America's appeal expected by Tuesday.

The findings suggest that government officials are using the stress tests to send a tough message to struggling banks. Bank of America and Citigroup have been the highest-profile problem children in recent months, but it is unlikely that they are the only banks the Federal Reserve has determined might need more capital.