WASHINGTON | Interest rates on short-term Treasury bills fell to the lowest levels in two weeks in Monday's auction.

The Treasury Department auctioned $26 billion in three-month bills at a discount rate of 0.12 percent, down from 0.15 percent last week. Another $27 billion in six-month bills was auctioned at a discount rate of 0.29 percent, down from 0.32 percent last week.

The three-month rate was the lowest since three-month bills averaged 0.05 percent on Dec. 29. The six-month rate was the lowest since 0.25 percent, also on Dec. 29.

The discount rates reflect that the bills sell for less than face value. For a $10,000 bill, the three-month price was $9,996.97 while a six-month bill sold for $9,985.34. That would equal an annualized rate of 0.122 percent for the three-month bills and 0.294 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, rose to 0.44 percent last week from 0.37 percent the previous week.