Interest rates on Treasuries follow market interest rates up and down. There is usually a spread between Treasuries of a given maturity and the same maturity private debt because investors perceive lower default risk on Treasuries. However, Treasuries move up and down with market interest rates. Here is the 3-month Treasury Bill rate:
So the capital value of Treasuries moves inversely with interest rates, just like the capital value of other assets. If market interest rates rise, then the capital value (i.e., the market price) of Treasuries will fall. One factor that makes market interest rates rise is unanticipated price inflation.So if price inflation picks up and investors haven’t built it into interest rates already, then the prices of existing securities, including Treasuries, will fall.