Home mortgage rates could fall to near 9 percent by next spring, their lowest level since early 1987, an economist with the Federal National Mortgage Association, known as Fannie Mae, said.

David W. Berson, chief economist, said the lower rates and an expected renewal of consumer confidence could begin to revive the single-family housing market beginning next summer.Berson, who spoke at a year-end briefing on the housing industry, said interest rates on 30-year, fixed-rate mortgages would decline to nearly 9 percent as a result of lower inflation and easing of monetary policy by the Federal Reserve Board.

Although home sales will remain sluggish through the first part of the year, Berson said he expects enough of an increase during the second half of 1991 to bring total home sales close to this year's level.

He said, however, that starts of new housing units would continue to be weak, falling to 1.12 million units from 1.20 million units in 1990.

"The housing sector will have to see more homes being sold on a sustained basis before beginning new construction," he said. "Stronger home sales in the second half of next year could lead to higher housing starts in 1992."

Single-family mortgage originations should climb by more than 7 percent in 1991, Berson said.

"This rise, coming on the heels of an estimated 3 percent drop in 1990, will result from stronger home sales in the second half of the year and a faster pace of mortgage refinancings. Borrowers will take advantage of the lowest interest rates in four years," he said.

However, even if an industry recovery begins by mid-year, Berson said significant regional variations in housing markets would continue.

If consumer confidence does not rebound, or if depository institution lending is curtailed significantly, the current slowdown could be more prolonged and more pronounced.

Another Fannie Mae official said mortgage funds will be abundant for lenders and home buyers next year, despite the current difficult economic environment.