U.S. diesel prices are up slightly from last week at less than 3 cents more per gallon, to $3.854.

Gas prices for the nation are up by less than half a cent to $3.39. Both diesel and gas prices have risen slightly since the beginning of January, from $3.783 for diesel and $3.299 for gas.

The only drop in prices, for both diesel and gas, was in the Rocky Mountains, where diesel dropped 2 cents and gas prices dropped by less than a cent.

The highest diesel prices were seen in California, at $4.116; the lowest in the Midwest at $3.746. The national average is 44.7 cents per gallon higher than a year ago.

Light, sweet crude for February delivery went up 2% to $100.71 a barrel on the New York Mercantile Exchange. Brent crude on the ICE futures exchange recently traded up 10 cents, or 0.1% to $111.44 a barrel.

The rise in crude prices is attributed to the promise of an Iranian oil embargo in Europe and economic growth in China.

The world's second-largest crude consumer, China's economy grew 8.9% in the fourth quarter, which helped ease concerns about an oil demand slowdown. Although the figure was smaller than a year ago, it was higher than the expectations of analysts and remains well above rates in the U.S. and Europe.