A slowdown in spending on plants and equipment in the United States and market jitters pulled crude oil down sharply lower in early Friday trading.

Crude oil prices passed the psychological threshold of $50 per barrel early in the session Thursday as data show diminishing stockpiles in the United States. Demand pressures and dwindling supplies from Canada, the top crude oil exporter to the United States, explained part of this week's rally.

U.S. labor figures show employment prospects continue to improve. The federal government revised first quarter growth in gross domestic product upward slightly to 0.8 percent, noting positive contributions from state and local government spending, as well as personal consumption expenditures.

Negative pressure, however, came primarily from a larger decrease in non-residential fixed investment, an indication of spending on plants and equipment. U.S. fourth quarter GDP increased 1.4 percent.

Crude oil prices fell back below the $50 mark in early trading Friday on the news. The price for Brent crude oil was lower by 1.5 percent to start the day at $48.83 per barrel. West Texas Intermediate, the U.S. benchmark price for crude oil, dropped 1.2 percent to $48.87 per barrel.

The rally may be taking a pause as traders wait for key metrics and indicators out later Friday. Baker Hughes releases its weekly snapshot of activity on the exploration and production side of the energy sector and U.S. Federal Reserve Chair Janet Yellen speaks early in the afternoon with Bloomberg News in what may be a preview of much-watched interest rate activity planned for the summer.

Next week, members of the Organization of Petroleum Exporting Countries sit down for their first round of talks since a proposal to keep production levels at January levels collapsed when Iran said it wanted to regain a share of the market lost to sanctions.

Analysis from UBS, cited in the Wall Street Journal, finds OPEC production is on the rise. The Swiss financial services group said a surplus could return to the market, pushing oil back toward the $40 mark in the short term.