Even as the government moves to plug holes in the nation’s banks, new gaps keep appearing.

As two financial giants, Citigroup and Merrill Lynch, reported fresh multibillion-dollar losses on Thursday, the industry passed a grim milestone: All of the combined profits that major banks earned in recent years have vanished.

Since mid-2007, when the credit crisis erupted, the country’s nine largest banks have written down the value of their troubled assets by a combined $323 billion. With a recession looming, the pain is unlikely to end there. The problems that began with home mortgages, analysts say, are migrating to auto, credit card and commercial real estate loans.

The deepening red ink underscores a crucial question about the government’s plan: Will lenders deploy their new-found capital quickly, as the Treasury hopes, and unlock the flow of credit through the economy? Or will they hoard the money to protect themselves?

John A. Thain, the chief executive of Merrill Lynch, said on Thursday that banks were unlikely to act swiftly. Executives at other banks privately expressed a similar view.