U.S. Steel Corp. officials said yesterday that the company may have to close its century-old steel mill on Chicago's Southeast side because of continuing losses, a move that could throw as many as 8,000 persons out of jobs.

The nation's largest steel maker also said it will cut its white collar work force in the midwest by 10 to 20 per cent over the next months, or by as many as 1,000 jobs.

U.S. Steel officials blamed big increases in low-priced steel imports, especially of heavy structural shapes used in construction, for most of the problems of the plant in Chicago.

U.S. Steel, like most domestic steel makers, has seen its profits shrink in part because of a continuing lag in business capital spending and in part because of a big influx of foreign steel, especially from Japanese.

Last week Bethlehem Steel Corp., the nation's second biggest producer and probably the most financially troubled of the major steel makers, said it would cut its steel making capacity by 2.6 million tons a year and reduce its work force by 7,300 in an attempt to improve its profitability.

A spokesman for U.S. Steel in Chicago said the company had not reached a final decision on whether to close the South Chicago Works, which has 12,300 employees, including about 8,000 blue-collar workers either at work, on shortened workweeks or temporarily laid-off.

When the steel industry was operating at top capacity in 1974 the South Chicago plant had 10,650 production workers and shipped about 169,000 tons a month. This year employment had averaged 8,5000 a month - lower in recent months - and shipments have averaged 105,000 tons a month.

This month about 6,500 production workers have jobs in South Chicago, 2,000 of them working short weeks because of a decline in demand.

Robert N. Clifford, assistant general superintendent of the South Chicago Works, told reporters yesterday that the entire steel industry is looking at its plants that are hard hit by imports and "is thinking of shutting them down rather than sustaining continued losses."