Economists forecast that the purchasing manager's index rose to 52 in September from 51.5, according to Bloomberg.
A reading above 50 indicates that business activity is still in expansionary territory.
Four of the five readings of the business barometer fell from July to August; only the employment component increased.
"On a trend basis, though, the July-August growth rates paint a slightly better picture - albeit still weak - than that seen earlier in the year," said Lorena Castellanos, senior economist at MNI Indicators, in the previous report.