experts predict that tens of thousands of Americans will not be able to, leaving a gaping hole at ailing banks still trying to recover from the housing bust.

The bank stress test, released last Thursday, found that the nation’s 19 biggest banks could expect nearly $82.4 billion in credit card losses by the end of 2010 under what federal regulators called a “worst-case” economic situation.

But if unemployment breaches 10 percent, as many economists predict, the rate of uncollectible balances at some banks could far exceed that level. At American Express, Citigroup, and J.P. Morgan Chase, one-fifth of the credit card balances are expected to go bad over the next 20 months, according to stress test results. At Bank of America and Wells Fargo, about a quarter of card loans are expected to sour.

Even the government’s grim projections may vastly understate the size of the banks’ credit card troubles. According to estimates by Oliver Wyman, a management consulting firm, card losses at the nation’s biggest banks could exceed $141.5 billion by 2010 if the regulators’ loss rate was applied to their entire credit card business. It could reach $180 billion for the entire credit card industry.

Regulators only published losses on credit cards held on bank balance sheets in the official stress test results. The $82.4 billion figure did not reflect another element included in their analysis: tens of billions of dollars losses tied to credit card loans that the banks packaged into bonds and held their off-balance sheets.

What is more, the peak unemployment level that regulators used to drive their loss estimates was not much worse than what current rates are on track to reach. That suggests the test results could reflect actual losses, rather than the worst-case scenario that regulators projected.

And many economists expect the number of job losses to climb even higher. On Friday, the unemployment rate reached 8.9 percent as the economy lost 539,000 jobs. The unemployment rate and the rate of credit-card charge offs, bank lingo for uncollectible balances, are traditionally closely aligned because consumers that lose their jobs are more likely to miss their payments.

Banks wrote off an average of 5.5 percent of their credit card balances in 2008, while the average unemployment rate was 5.8 percent. By the end of the year, the rate of credit-card write-offs was 6.3 percent; more recent data was not available.

Experts predict that the rate of credit-card losses could eventually surpass the jobless rate because of the compounding effects of the housing crisis and lackluster consumer confidence. Shortly after the technology bubble burst in 2001, credit card loss rates peaked at 7.9 percent.

“We will blow right through it,” said Inderpreet Batra, a partner at Oliver Wyman, a consultancy specializing in financial services.

After writing-off about $45 billion in bad debts during 2008, credit card lenders are bracing for the worst year in the industry’s history. Not only are losses spiraling, but lawmakers are on the verge of passing a set of tough new consumer protections that could have a devastating effect on profits. This week, the Senate is expected to take up the so-called Credit Cardholders Bill of Rights after the measure passed in the House with a strong bipartisan vote of 357 to 70.