Insurance giant AIG has reported a loss of $61.7bn (£43bn) in the final three months of 2008 - the largest quarterly loss in corporate history.
And the firm will receive an extra $30bn from the US government as part of a revamped rescue package.
AIG has already received $150bn in financial support - the biggest bail-out by far of any US company.
Stock markets slid sharply as AIG's plight underscored fears about the health of the global financial system.
The Federal Reserve and the Treasury said that AIG posed a "systemic risk" to the global financial system.
"The potential cost to the economy and the taxpayer of government inaction would be extremely high," they said.
"The additional resources will help stabilise the company, and in doing so help to stabilise the financial system."
As well as insuring households, AIG plays a key role in insuring risk for financial institutions around the world.
The news of AIG's historic loss comes as HSBC, Europe's biggest bank, seeks to raise £12.5bn ($17.7bn) to strengthen its finances following a 62% fall in annual profit.
AIG - $180bn
Bank of America - $45bn
Citigroup - $50bn
JP Morgan Chase - $25bn
Wells Fargo - $25bn
Goldman Sachs - $10bn
Morgan Stanley - $10bn
State Street - $3bn
Bank of New York Mellon - $3bn