The Purchasing Managers Index for U.S. manufacturing showed the monthly average for the July through September period was the lowest for a third quarter since 2009.
Although the headline PMI index was unchanged from August at 51.5, manufacturing output rose at slowest pace in September in three years, Markit said.
In August, the PMI rose from 51.4 to 51.9. The break even point between growth and contraction is 50. A flash estimate, which was released Thursday, indicates that 85 percent of the pertinent data are available.
Markit said the output index slid from 51.9 in August to 51.2 in September. The new orders index, however, rose from 51.9 in August to 52.4 in September.
The employment index showed slightly faster growth with a reading of 52.7 compared with 52.4 in August.
Markit Senior Economist Chris Williamson said U.S. manufacturers "reported another tough month of business conditions ... rounding out the worst quarter in three years."
"Gross domestic product therefore looks likely to have expanded at a much weaker pace than the 1.7% annualized rate seen in the second quarter, slipping closer towards stagnation," he said in a statement.