With numbers above 50 indicating growth, Markit said the flash purchasing managers index for U.S. manufacturing, which could be revised later, dropped from 55 in December to 53.7 in January -- slightly higher than the average for 2013, 53.5.
Markit said the January measure indicates "solid underlying growth across the U.S. manufacturing sector."
"Extreme weather," in January contributed the "sharpest lengthening of suppliers' delivery times since August 2008," Markit said.
Markit said the index for new orders remained positive, but slipped from 56.1 to 54.1. The new export orders index dropped from a slightly positive 51.4 to a negative 48.9. The index measuring the number of employees dropped slightly from 54 to 53.2.
"The flash PMI indicates that the manufacturing sector continued to grow at the start of 2014, and that the underlying trend most likely remained reassuringly robust," said Markit Chief Economist Chris Williamson said in a statement.
"After allowing for companies that saw production and sales disrupted by the cold weather, the rate of growth of output and orders remained as strong, if not stronger, than seen late last year. Output looks to be growing at an underlying rate of 2 percent per quarter, which is generating ongoing robust job creation of around 10,000 per month," he said.