General Motors Corp, which has lost $51 billion in the last three years (yes, that’s right, $51 billion) and is trying to cut costs and restructure yet again, said yesterday it will try to sell up to $4 billion in assets.

That’s a lot of $$ to raise from asset sales. In fact, it’s almost as much as the automaker’s market cap of about $5.6 billion.

So what can it sell? We know it is already reviewing its Hummer brand — and a sale is likely. But with skyrocketing gas prices and a huge slump in demand in the U.S., Hummer, with its 9-14 miles per gallon, will probably not even net GM $1 billion.

What else could it sell? A sale of Onstar, its vehicle communications system, is possible. A sale of its remaining 49-percent stake in its finance arm, GMAC, is also possible. But what is most likely is that GM — often criticized for having too many brands — will try to offload more brands.

Next likely to come under scrutiny (even though GM has said no other brands are for sale) are Saturn — a fading-but-recently-revived brand made more attractive with an independent dealer network — and Saab —  a Swedish “near-luxury” brand which has the disadvantage of being “neither here nor there,” as some investment bankers have said. (It doesn’t have the premium luxury positioning but lacks the scale of a mass-market brand).

But here’s the real conundrum: Potential buyers for the brands would have to be from overseas — a foreign automaker who wants to gain a presence in the U.S. auto market. As U.S. vehicle sales fall to their lowest levels in 15 years and U.S. automakers are cutting production to align with ever-falling demand, it wouldn’t make much sense to help more automakers come into the market and expand their presence here.

That would only end up putting more pressure on profit margins for everyone. It would force the Big Three to cut production further. It would create more competition and more capacity amid slipping demand. It would give a new competitor a space, a dealer network and a platform to grow in a market that is already hurting the Big Three U.S. automakers so much that analysts are wondering if a bankruptcy is on the horizon.

So it doesn’t really make sense. Besides, with GM having said it needs to raise capital by selling assets, potential buyers are likely to lowball offers. But then again, GM needs the cash. Sure, it has $24 billion in cash on hand, but the automaker is burning through a few billion every quarter.

Desperate times call for desperate measures.