WASHINGTON (AP) - Interest rates on short-term Treasury bills rose in Monday's auction to the highest levels since February.

The Treasury Department auctioned $24 billion in three-month bills at a discount rate of 1.800 percent, up from 1.610 percent last week. Another $23 billion in six-month bills was auctioned at a discount rate of 1.850 percent, up from 1.740 percent last week.

The three-month rate was the highest since three-month bills averaged 2.160 percent on Feb. 25. The six-month rate was the highest since 2.070 percent, also on Feb. 25.

The discount rates reflect that the bills sell for less than face value. For a $10,000 bill, the three-month price was $9,954.50 while a six-month bill sold for $9,906.47.

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 slightly to 1.94 percent last week from 1.93 percent the previous week.