WILMINGTON, Del. (AP) _ Du Pont Co. is eliminating up to 4,500 more U.S. jobs by the middle of next year to cut costs.

Du Pont's nylon business will take the hardest hit, losing 1,600 jobs. About 700 of the 1,300 workers at its Martinsville, Va., nylon plant will be let go by mid-1994. About 275 jobs will be lost at nylon plants in Delaware.

The chemical giant said Monday that other job losses would be spread through all sectors of the company except its energy subsidiary, Conoco.

Du Pont had 133,000 employees worldwide in 1990. Since then, about 9,000 have taken advantage of early leave offers. Du Pont announced 1,300 layoffs earlier this year because of corporate streamlining and consolidations.

D. John Ogren, senior vice president, said the cuts are necessary to keep Du Pont competitive.

DuPont expects the employee reduction costs will result in an after-tax charge against earnings of about $375 million, or 56 cents per share, in the third quarter. DuPont said it also anticipates other restructuring charges of undetermined size in the third quarter.

In May, the company consolidated 40 to 50 divisions into 18 business units - such as nylon, medical products, printing and publishing - and eliminated the need for some jobs.

The cuts haven't really made an impact in earnings, one analyst says.

''Unfortunately, the economy has been week,'' said Jeff Spetalnick, an analyst with Oppenheimer & Co. in New York.

DuPont's European operations also have embarked on an additional $500 million cost-reduction effort to be completed next year,

In trading Monday on the New York Stock Exchange, DuPont closed at $49.62 a share, up $1.75.