WASHINGTON (AP) — The average rate in the U.S. on a 30-year fixed mortgage rose above 4 percent for the first time in more than three months. The sharp increase suggests the window to buy or refinance a home at historically low rates is closing.

Mortgage buyer Freddie Mac says the rate on the 30-year loan jumped to 4.08 percent, up from 3.92 percent the previous week. A month ago, it touched 3.87 percent, the lowest since long-term mortgages began in the 1950s.

The average on the 15-year fixed mortgage rose to 3.30 percent, up from 3.16 percent last week and a record low of 3.13 percent two weeks ago.

The low rates have been among the positive signs that suggest the housing market could pick up this year.