HSBC recently announced heavy job cuts
Losses at Europe's biggest bank, HSBC, relating to the US housing market crisis reached $4.3bn (£2.7bn) in the third quarter.
The unprecedented turbulence in financial markets continued to present "enormous challenges", the bank added.
HSBC said it was still unclear whether there were "further risks to be uncovered" in the financial sector.
Elsewhere, its battered investment banking business took a $600m hit due to credit crunch losses.
The bank recently announced it was cutting 1,100 jobs worldwide because of the current financial turmoil.
HSBC said its US losses reflected the continuing weak housing market and rising level of unemployment.
The new US losses come on top of a $3.6bn write-down in the second quarter.
In a trading statment, HSBC said its profit for the third quarter was higher than during the equivalent period in 2007, without giving precise figures.
For the nine months ended 30 September 2008, pre-tax profit was lower than in the equivalent period in 2007, it added.
Group chief executive, Michael Geoghegan, said: "These are extraordinary times in our industry."
He said HSBC's US results were largely in-line with its expectations, but "current trends point to further deterioration in the near to medium term".
The bank said that its asset sales and growth in Asia helped offset the worsening US economy.
"These numbers are something of a mixed bag, bringing another set of US home loan write-downs," said Richard Hunter, analyst at Hargreaves Lansdown stockbrokers.
"On the other hand, the contribution from its Asian operations has very much cushioned the blow."
Shares in HSBC fell by 1% to 738.5p in early trading.