The U.S. manufacturing sector continued to expand in December but its growth rate hit an 11-month low, an industry report showed on Tuesday.

Financial data firm Markit said its preliminary or "flash" U.S. Manufacturing Purchasing Managers Index fell to 53.7 in December, matching the 2014 January low when severe weather impacted economic activity.

Economists polled by Reuters had expected the December reading at 55.2, which compares to November's 54.8 final reading.

A reading above 50 signals expansion in economic activity.

The December output subindex fell to 54.7, also the lowest since January, from last month's 55.6 final reading.

The employment subindex dipped to 52.8 from 55.1. It was the lowest since July but also the 18th straight month of readings indicating growth in jobs.

"Softer output and employment numbers merely represent a cooling in the pace of expansion from unusually strong rates earlier in the year," said Chris Williamson, chief economist at Markit, in a statement.

He said, however, the data "also send a warning light to policymakers that the fourth quarter is likely to see a weakening in the pace of economic growth."

Markit's "flash" reading is based on replies from about 85 percent of the U.S. manufacturers surveyed.