U.S. industrial production unexpectedly dipped in December, the Federal Reserve said on Friday, as a drop in auto production held back overall output.

The Fed said production at U.S. factories, mines and utilities fell 0.2 percent in the month. Industrial capacity in use also slipped, to 75.4 percent from 75.6 percent. Both readings were weaker than Wall Street analysts had been anticipating and showed the embattled factory sector ended a tough year on a downbeat note.

A sharp downshift in auto production accounted for the December output decline. The Fed said auto production fell 4.7 percent in the month while overall output excluding autos actually posted a slight gain, rising 0.2 percent.

Analysts polled by Reuters had expected December production to be up by 0.3 percent and capacity in use to rise to 75.8 percent.