Three out of four of the nation's top business economists now believe the United States has skidded into a recession, in part because of the rapid rise in oil prices following the Iraqi invasion of Kuwait.

The report from the National Association of Business Economists reflects a sharp jump in pessimism among its 51 professional forecasters, who just three months ago still believed the country could avoid a downturn.

Other reports released yesterday -- continued drops in home sales and consumer confidence -- offered fresh support for the economists' mood shift.

"In our view the economy was on a slow-growth track prior to the invasion of Kuwait" on Aug. 2, Richard D. Rippe, NABE president and chief economist with Dean Witter Reynolds Inc., said at a news conference yesterday. "That slow-growth track has been converted into a mild recession outlook by the oil-price shock that has developed."

One economic indicator that seemed to respond directly to the Kuwait invasion was the index of consumer confidence. The Conference Board reported it sank further in its November survey, to levels near the depths of the 1982 recession.

The board said it found more people expecting higher unemployment and weaker business conditions in the coming months, along with fresh evidence that consumers are paring their spending plans heading into the Christmas shopping season.

Fabian Linden, a Conference Board economist, said consumer confidence "is now only marginally above the figure recorded during the lowest point of the 1982 economic downturn."

The business research organization said its monthly consumer confidence index, which registered 115.1 in November 1989, fell to 61.5 this month from 62.6 in October.

Perhaps the weakest sector of the economy recently has been housing, and another report indicated it was getting weaker still. The National Association of Realtors said sales of existing homes fell 4.7 percent in October to their lowest level in nearly six years.

The real estate group also said the national median price of an existing house also fell in October, down 1.7 percent to $92,800. The median means half of the homes cost more, half less.

Each region of the country reported declines in sales and all but the West also posted lower median prices.

The only bright economic news yesterday seemed to come out of Detroit, were the Big Three automakers said yesterday their mid-November sales of North American-made vehicles ran 13.4 percent ahead of a slow period a year ago. Sales for the year, however, trail last year by 6.6 percent.

Analysts said much of the mid-November increase was the result of a surge in fleet sales -- bulk sales of vehicles to rental car companies and companies that maintain large fleets.

The auto companies are not expecting any big surge in orders in the near future. Starting this week, the Big Three had 38,000 employees on temporary layoffs at 14 assembly plants in eight states.

Despite the generally gloomy news, Rippe, the president of the business economists, said any recession "should be shallow by historical standards." The median estimate of the forecasters is for economic growth to decline 1.0 percent in this quarter and 0.8 percent in the next.

In his group's survey, 45 percent of the forecasters said a recession either had begun or was imminent. Just a year ago, 62 percent of the forecasters predicted the economy would escape a recession through 1992.

While two-thirds of the group believe the downturn will last two quarters or less, 29 percent said it would continue for three quarters. None believed it would last beyond a year.

The last recession lasted 16 months, from July 1981 to November 1982.

Rippe said "one key assumption in our economic outlook" is the prospect that oil prices will fall and "diminish the tax on the economy ... and help reduce the rate of inflation."