Reuters reports that the U.S. government will have to pump “much more money into banks than the $700 billion it has committed if they are to survive the downturn, even if the cost is a tough pill for taxpayers to swallow.” Something Hank Paulson failed to mention on his recent interview with Charlie Rose.

That’s because the amount of writedowns and losses from bad mortgages predicted for banks globally is expected to total $1.5 trillion. U.S commercial banks, however, have a total capital of only $1 trillion. This from Reuters:

Admittedly not all of those will be in the United States, and banks will generate capital in the coming years even as they write down assets and set aside more money for losses. But add in expected losses from commercial real estate, leveraged loans, credit cards, auto loans and a host of other areas as economic growth slows, and even the Treasury’s full $700 billion Troubled Assets Relief Program starts to look worryingly small.

But if $700 billion from the government is not enough, don’t expect investors to make up the difference — they aren’t interested in pouring money into a banking system that would otherwise be insolvent. That’s why pumping in enough money to keep the banking system solvent is key, experts said.

Oddly, Paulson refers throughout the interview to bailout money going to “healthy banks.”

It seems like an obvious point to make, but if banks are so healthy, Hank, why do they need $700 billion in taxpayers’ money?

Watch it here.