Interest rates rise at weekly auction of US Treasury bills

Interest rates on short-term Treasury bills rose in Monday's auction, with rates on six-month bills climbing to their highest level since late May.

The Treasury Department auctioned $40 billion in three-month bills at a discount rate of 0.310 percent, up from 0.300 percent last week. Another $34 billion in six-month bills was auctioned at a discount rate of 0.450 percent, up from 0.445 percent last week.

The three-month rate was the highest since those bills averaged 0.320 percent four weeks ago on July 25. The six-month rate was the highest since those bills averaged 0.475 percent on May 31.

The discount rates reflect that the bills sell for less than face value. For a $10,000 bill, the three-month price was $9,992.08, while a six-month bill sold for $9,977.25. That would equal an annualized rate of 0.315 percent for the three-month bills and 0.457 percent for the six-month bills.

Separately, the Federal Reserve said Monday that the average yield for one-year Treasury bills, a popular index for making changes in adjustable-rate mortgages, edged up to 0.58 percent last week from 0.56 percent the previous week.