The average rate on 30-year fixed mortgages rose this week to the highest level in seven months, reflecting higher yields on long-term Treasurys.
Freddie Mac says the rate increased to 4.86 percent from 4.81 percent in the previous week. It hit a 40-year low of 4.17 percent last month.
The average rate on the 15-year loan rose to 4.20 percent from 4.15 percent - the highest reading in six months.
It fell to 3.57 percent in November, the lowest level on records starting in 1991.
Rates have been rising since November as investors shift money out of Treasurys and into stocks.
Many expect the tax-cut plan will fuel economic growth and increase inflation.
Yields tend to rise on fears of inflation.
Mortgage rates track the yields on the 10-year Treasury note.