WASHINGTON (AP) -- Interest rates on short-term Treasury bills fell in Monday's auction to the lowest levels since December.

The Treasury Department auctioned $35 billion in three-month bills at a discount rate of 0.065 percent, down from 0.075 percent last week. Another $30 billion in six-month bills was auctioned at a discount rate of 0.095 percent, down from 0.105 percent last week.

The three-month rate was the lowest since these bills averaged 0.040 percent on Dec. 17. The six-month rate was the lowest since these bills averaged 0.090 percent, also on Dec. 17.

The discount rates reflect that the bills sell for less than face value. For a $10,000 bill, the three-month price was $9,998.36 while a six-month bill sold for $9,995.20. That would equal an annualized rate of 0.066 percent for the three-month bills and 0.096 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 down to 0.13 percent last week from 0.14 percent the previous week.

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