WASHINGTON — Federal environmental regulators said Friday they had denied three industry petitions asking the government to reconsider the recently implemented diesel-emissions regulations.

The Bush administration previously said it would enforce the rule. But the American Petroleum Institute, the American Trucking Association and Mack Trucks/Volvo Powertrain had each petitioned the Environmental Protection Agency to take another look. According to an Associated Press report, the EPA refused, saying Friday only that its decision was based on “a review of arguments” by the petitioners.

The new diesel rule, which went into effect in March, requires refiners to reduce the sulfur content of highway diesel fuel by 97 percent between 2006 and 2009. Trucks and buses starting with model-year 2007 will have to be equipped with engines that reduce emissions of particle soot by 90 percent. Nitrogen oxide emissions from diesel engines will have to be reduced by 95 percent by the 2010 model year. EPA has estimated the rule will raise the price of new diesel vehicles by $1,200 to $1,900, and of diesel fuel by four to five cents a gallon.

Industry representatives have fought for a change in the regulations that would eliminate the slow phase-in of new diesel requirements, saying they place additional pressure on their ability to produce, store and distribute multiple grades of fuel during the phase-in periods.