Oil futures rose to an all-time high near $121 a barrel Tuesday with new concerns about a threat to supply and a weaker dollar. The surge in oil prices was also fueled by hopes that the U.S. economy will be spared a sharp downturn after the release of data Monday showing an unexpected expansion in the U.S. service sector in April, analysts said. Light, sweet crude for June delivery rose to a record $120.93 a barrel in electronic trading on the New York Mercantile Exchange on Tuesday. The contract later retreated to $119.88 a barrel, down 9 cents from Monday's close.