Ford Motor Co. set a world auto industry record for earnings in a single quarter, but suffered a decline in U.S. earnings, the nation's second-largest automaker said Thursday in reporting its figures for the first quarter.

Ford's earnings of $1.623 billion, or $3.31 a share, on sales of $20.74 billion were up 8.8 percent over first quarter 1987 earnings of $1.49 billion, or $2.87 a share, on sales of $18.14 billion.The previous quarterly record was set by General Motors Corp., with $1.614 billion in profits in first quarter 1984.

Ford profits earned in the United States fell 10.2 percent in the first quarter to $1.04 billion from $1.16 billion in first quarter 1987.

But the drop in U.S. earnings was offset by record overseas earnings, which jumped nearly 76 percent to $580 million from $330 million in the first three months of 1987, Ford said.

On Wednesday, Chrysler Corp. reported first quarter earnings fell nearly 32 percent from a year ago - to $183.7 million, or 83 cents a share, from $269.4 million, or $1.24 a share, in the corresponding period a year ago.

Industry-leader GM earlier reported an 18 percent increase in first quarter earnings to $1.09 billion, or $3.11 a share. In the first quarter of 1987, GM had earnings of $922.5 million, or $2.62 a share.

However, GM's first quarter earnings would have fallen 6 percent without a one-time accounting change that added $224.2 million, or 70 cents a share.

Ford blamed the drop in U.S. earnings on the costs of introducing new products and running buyer incentive campaigns, which helped increase sales. Ford's U.S. car market share grew from a year ago by 1.8 percentage points to 21.8 percent.

Ford's truck market share grew slightly to 29.7 percent in the first quarter.

Ford's gross profit per unit and manufacturing profit per unit are far and away better than General Motors, said Joe Phillippi, analyst with Shearson Lehman Hutton Inc. In New York.

Mr. Phillippi said Ford's sales include a healthy percentage of high- profit vehicles while it has the best control over costs in the industry.

Ford's foreign performance was boosted in Europe by strong sales throughout the industry, improved profit margins and some changes in exchange rates.

In Latin America, the Autolatina joint venture Ford and Volkswagen formed in July 1987 helped earnings by reducing operating costs and cutting interest expenses and benefitted from improvements in the Brazilian economy.