U.S. consumer sentiment deteriorated in October as rising energy costs and persistent job worries made Americans less optimistic about the future, according to a survey released Friday.

The University of Michigan (search) said its consumer confidence index dropped to 91.7 in October, down from 94.2 in September but higher than a mid-month reading of 87.5, according to market sources who saw the subscription-only report.

"Confidence is down a little bit, it seems to be driven by concerns about oil and about the future," said Steve Gallagher, economist at SG Cowen Securities.

Analysts in a Reuters poll had forecast that the index would slip to 88.0. The measure of current conditions climbed to 104.0 from 103.7, while the expectations component slid to 83.8 from 88.0.

Consumer confidence is watched as a gauge of future spending, which accounts for two-thirds of the U.S. economy, although the correlation between sentiment and actual shopping patterns has not been strong in recent years.

The U.S. government said on Friday gross domestic product -- the broadest measure of economic growth -- grew 3.7 percent, below forecasts but still a strong showing, and one helped in part by a resilient consumer.

With the economy growing robustly, employment continues to be the missing piece of the recovery. Job growth has proved anemic in recent months, and analysts will scrutinize next week's payrolls report for an update on the labor market.