The Institute for Supply Management (ISM) said its index of national factory activity dipped to 50.8 from 51.6 the month before and missed expectations of 52.0, according to a Reuters poll of economists.
A reading below 50 indicates contraction in the manufacturing sector, while a number above 50 means expansion.
New orders rose to 52.4 from 49.6, while the prices paid index fell to its lowest level since April 2009 at 41.0 from 56.0. The employment index eased to 53.5 from 53.8.
(Reporting by Leah Schnurr, Editing by Chizu Nomiyama)