American International Group, Inc may need between $5 and $10 billion to bolster its balance sheet beyond the $20.3 billion it has already collected, according to a Citigroup analyst.

The world's largest insurer may need the funds rather than let its credit ratings be cut again, said Citigroup's Joshua Shanker.

``The ramifications of another downgrade would be devastating,'' he said. ``A downgrade would be so detrimental to AIG that it will not allow this to happen.''

Shanker wrote that chief executive Martin Sullivan needs to act quickly and decisively, to take AIG back into stability and profitability.

He lowered his price target for the stock to $41 from $47.

Shares of AIG fell $1.40, or 3.84 percent to $35.22.