Fixed mortgage rates on long-term loans in the United States abated slightly headed into a holiday weekend, the Federal Home Loan Mortgage Corp. said Thursday. For the week, the average 30-year fixed mortgage dropped from 3.66 percent to 3.59 percent with an average 0.6 points, Freddie Mac said. A year earlier, interest rates for 30-year, fixed-rate loans were at 4.22 percent. For 15-year loans in the week ending Thursday, interest rates fell from 2.89 percent to 2.86 percent with an average 0.6 points. A year ago, 15-year loan rates averaged 3.39 percent. Interest rates for five-year adjustable-rate mortgages rose from 2.8 percent to 2.78 percent in the week with 0.6 points. In the same week of 2011, rates for five-year ARM contracts stood at 2.96 percent. The average interest rates for one-year ARM contracts fell from 2.66 percent to 2.63 percent in the week with 0.4 points. Rates a year ago for one-year ARM contracts averaged 2.89 percent.