A combination of cash and 2008 earnings is being used by the French bank to fund the deal, which will help its US counterpart shore up its balance sheet.
After tax, Citi stands to earn around $4 billion from the sale.
The move comes in the wake of chief executive Vikram Pandit's pledge earlier this year to help the company "get fit" by selling off $400 billion of assets.
Citi has been one of the banks worst affected by the credit crunch, and has lost around $43 billion since the onset of the global financial crisis last summer.
"This [sale] is another strategic step in our effort to reorganize Citi, strengthen our balance sheet, and put us squarely on the path to future growth driven by our core businesses," Mr Pandit said in a statement.