The Department of Energy said Tuesday that diesel fuel prices will average just under $3 a gallon this year, but will rise above that level in 2011.

Diesel will average $2.97 this year and $3.14 next year, DOE said in its monthly short-term energy outlook. That forecast is down a cent and up a penny, respectively, from last month's outlook.

Gasoline will average $2.80 a gallon this summer, an increase of 36 cents from last summer. However, DOE forecasted gas to average $2.77 this year and $2.92 next year.

Diesel averaged $2.46 and gas averaged $2.35 a gallon last year, DOE said.

Crude oil prices averaged $76.32 per barrel on the New York Mercantile Exchange in July, up $1 from June and about in line with DOE's previous forecast of $77 per barrel.

DOE said crude will average $80 a barrel in the second half of this year before rising to $85 in 2011 - up $1 and $2, respectively, from its most recent forecast.