Ford Motor Co. announced yesterday that it suffered a net loss of $41 million in the final three months of 1979, even though earnings outside the United States increased almost four-fold in the same period.

The overall loss, Ford's first in five years, reflected lower automobile sales in the U.S. and Canada and higher foreign exchange costs worldwide.A year ago, Ford reported profits in the October-December quarter of $282 millin ($2.35 a share), and those results were depressed by a nine-week strike in Britain and the sale of one business.

Ford's sales in the final quarter fell 11 percent to $10 billion from $11.2 bilion, as the nation's second-largest auto manufacturer completed one of the most difficult North American sales periods in its history.

After taxes, Ford had a U.S. loss in the fourth quarter of $2.28 a share -- some $275 million -- compared with profits last year of $1.83 a share. Outside the United States Ford's fourth-quarter earnings rose to $1.93 a share from 52 cents.

For the year as a whole, Ford had its third best year on record, the result of record international automotive and financing profits. Because of sagging U.S. and Canadian sales, however, overall company earnings were cut by a quarter to $1.17 billion ($9.75 a share) from $1.59 billion ($13.35). Worldwide sales for the year advanced slightly to $43.5 billion from $42.8 billion.

Although company officials declined to provide figures, analysts said pre-tax losses by Ford's U.S. and Canadian automotive operations exceeded $1 billion for the year. The company said only that after-tax losses for the year from U.S. operations were $199 million ($1.66 a share).

In a statement, Ford President Philip Caldwell noted that Ford's non-U.S. earnings were a record 50 percent higher than in 1978. Earnings from operations outside the country, were $1.4 bilion (11.41 a share).

Losses in North American auto operations were offset partially by the financing subsidiary's record as well as favorable results from the glass, steel and aerospace businesses.

"The decline in U.S. automotive profitability reflected lower industry volume, a smaller Ford market share as demand in the marketplace shifted to smaller cars, the impact of inflation on the costs of labor and materials, the high cost of redesigning our product lineup, and increased marketing costs resulting from weaker consumer demand," Caldwell stated.

U.S. sales were down 12 percent from the prior year while overseas sales jumped 28 percent. U.S. sales were down 847,000 vehices while sales outside this country were up 230,000; overall, worldwide factory sales of cars, trucks and tractors totaled 5.94 million units, off 9 percent.

In other developments yesterday, the major U.S. auto manufacturers reported that car output this week is at the highest level of the year -- 164,797 cars, up 17 percent from a week ago. At the same time, layoffs are rising.

The auto firms said layoffs next week will increase to 196,350 from 185,600. Of the total, 20,950 are for a week or two and the rest are indefinite.