Bankers giveth, and bankers taketh away.

It is the latest in a series of debt commitments for M&A deals that banks are trying to back out of. Mortgage lender PHH said today that J.P. Morgan Chase and Lehman Brothers Holdings signaled they will back out of their commitment to fund Blackstone Group and General Electric’s purchase of PHH. The move may leave the buyers $750 million short of debt financing they need to complete the $1.8 billion deal. (Read more about it in an early Bloomberg take.)

Banks are pulling any levers they can to get out of lending commitments that have suddenly become unprofitable as credit markets sour. As we discussed Friday, a similar dynamic is playing out with Morgan Stanley’s financing of GSO’s $1.1 billion purchase of Reddy Ice. Finish Line’s leveraged purchase of athletic-shoe retailer Genesco, financed by UBS, smells the same.   

All these deals are relatively small ones. Things will get really interesting if and when the banks try to back out of their commitments on the really big deals, the ones like TXU (at $32 billion) and Alltel ($27.5 billion). Then the fireworks would really begin.