The U.S. Steel Corp., the nations largest steel-maker, agreed yesterday to pay a $4 million fine in settlement of a long-standing water pollution suit brought by the federal government and the state of Indiana.

The steel company, in a consent decree signed yesterday in U.S. District Court in Hammond, Ind., also agreed to pay additional $250,000 fine to end a criminal contempt case in which it was accused of violating the Clean Air Act of 1970.

The settlement of the air and water pollution cases are subject to public review and commitment for 30 days, after which a final decree will be issued by the court.

The $4 million penalty was the largest civil fine ever assessed in a water pollution case, according to the Envionmental Protection Agency. The biggest fine ever levited in a criminal water pollution case came last February against the Allied Chemical Corp. The chemical firm was penalized $13.2 million - later reduced to $5 million - for secretly discharging wastes from Kepone, a highly toxic pesticide, into Virginia's James River.

The water and air polution cases involving U.S. Steel began in 1974, and primarily affect the company's major steel works at Gary, Ind.

In the first, the company was accused of dumping 700 million gallons a day of polluted water - containing cyanide, fluoride, ammonia, chlorides, sulfates and other chemicals - into Lake Michigan and one of its tributaries, the Grand Calumet River.

As part of settlement, U.S. Steel was given until Aug. 1, 1980, to complete construction of a $70 million water pollution control plant that is expected to recycle 65 million gallons of waste water daily.

EPA Said the penalty was assessed because U.S. Steel admitted it will not be able to complete construction of the pollution-control facility before July 1, 1977, the original deadline.

Of the $4 million fine issued in the water pollution dispute, $2,925,000 would go to thew federal government, $325,000 is expected to be paid to Indiana's Environmental Management Fund, $500,000 is slated to be spent by U.S. Steel on environmental research, and $25,000 is expected to go to the University of Michigan for environmental impact studies of Lake Michigan.

In the air-pullution matter, U.S. Steel was given until July 15, the meet state air standards at its Gary steel works and its nearby Universal Atlas Cement Plant. The company had failed to meet 1976 deadlines to correct air-pollution problems at the plants, according to the EPA.