Below is my response to a reader of my blog, who asked about the implications of China reducing its holdings of US treasury debt.
I think that in the simplest terms, China is exiting the market for US Treasuries, which means that the US government must offer a larger yield in order to entice buyers who are still in the market to make up for the loss of Chinese demand. That means that US interest rates would have to rise, because the T Bill is the base upon which all other rates are set. Why would someone buy a corporate bond at a lower yield when he can buy a T Bill, which has less risk, for the same or even higher yield? Alternatively, the Fed could monetize the debt, which would cause US prices to rise (eventually) due to the increase in the money supply.
I have contended for some time that this event would lead to a crisis. When the world market eschews T Bills, the government is left with difficult choices. It can raise taxes to pay off the debt that it can't roll over. It can cut spending to decrease the amount of debt that is required to fund all the government's programs. It can increase interest rates to suck more money out of the private economy and into government bonds. Or it can monetize the whole thing. Of course, it could do a combination of all these things. My least favorite option is that the government monetizes the debt; i. e., prints more money. My favorite option is for government to drastically reduce its expenditures, but this is probably the most politically difficult option.