U.S. Steel Corp. plans to close its Electrical Cable Division plant in 10 days, leaving 500 employees jobless.

W.E. Chase Jr., division general manager, said the closing was due to a strike by about 350 United Steelworkers Union employees which has shut down the plant since Aug. 1.

Chase said the decision to close Oct. 15 is irrevocable. He said settlement last Sunday, and said it included a general wage increase, significant benefit improvements, an additional holiday off and a $150 bonus.

Edward F. O'Leary, president of USW Local 1885, said, "We have attempted to do everything in our power to keep that plant in the City as asking the company to open their of Worcester. We even went as far books and show us where they were in trouble, and we would give them the relief they were seeking, even to the point of taking further cuts.

"The company refused. Because of this the union could only figure that the company was making one hell of a profit an didn't want give it up."

Meanwhile in St. Louis, McDonnell Douglas Corp. said it will lay off about 900 of 1,500 employees before the end of next January at its Tico plant in Titusville, Fla. The company said the deduction was caused by completion of a contract for production of Dragon anti-tank missiles for the U.S. Army.