Interest rates on short-term Treasury bills fell in Monday’s auction to the lowest levels since late January.

The Treasury Department auctioned $28 billion in three-month bills at a discount rate of 0.18 percent, down from 0.20 percent last week. Another $27 billion in six-month bills was auctioned at a discount rate of 0.37 percent, down from 0.40 percent last week.

The three-month rate was the lowest since those bills averaged 0.15 percent on Jan. 26. The six-month rate was the lowest since they averaged 0.345 percent, also on Jan. 26.

The discount rates reflect that the bills sell for less than face value. For a $10,000 bill, the three-month price was $9,995.45, while a six-month bill sold for $9,981.29. That would equal an annualized rate of 0.183 percent for the three-month bills, and 0.376 percent for the six-month bills.

Separately, the Federal Reserve said the average yield for one-year Treasury bills, a popular index for making changes in adjustable rate mortgages, rose to 0.60 percent last week from 0.58 percent the previous week.

Copyright 2009 The Associated Press.