WASHINGTON (AP) _ Interest rates on short-term Treasury bills rose in Monday's auction with six-month bills climbing to the highest level since early March.

The Treasury Department auctioned $20 billion in three-month bills at a discount rate of 1.420 percent, up from 1.320 percent last week. Another $20 billion in six-month bills was auctioned at a discount rate of 1.700 percent, up from 1.680 percent last week.

The three-month rate was the highest since three-month bills averaged 1.450 percent on April 7. The six-month rate was the highest since 1.810 percent on March 3.

The discount rates reflect that the bills sell for less than face value. For a $10,000 bill, the three-month price was $9,964.11 while a six-month bill sold for $9,914.06.

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 1.88 percent last week from 1.67 percent the previous week.

Copyright 2008 The Associated Press.