WASHINGTON, D.C. --- President Bush and Congress seem to be on a collision course in the quest to raise fuel-efficiency standards, according to a report from the Washington Post. Transportation Secretary Mary Peters said Wednesday that Bush would oppose Congressional plans to raise fuel-efficiency standards if the approach differs markedly from that of the administration. Bush on Tuesday advocated changing standards to save 8.5 billion gallons of gasoline by 2017. Scientists estimate that Bush's plan would require automakers to lift overall fuel efficiency to 34 miles per gallon, from today's 24 mpg. But lawmakers from both parties are starting to push for higher standards than that. Sen. Ted Stevens (R-Alaska) has introduced a bill that would bolster the passenger-car standard to 40 mpg. The government's average fuel-economy standard for passenger cars has been 27.5 mpg since the 1980s. Peters told the Post that Bush favors changing how the government regulates fuel economy for passenger cars. At present, Congress sets standards for cars, while the administration sets them for trucks and SUVs. Bush wants the National Highway Safety Administration to assume responsibility for setting fuel-efficiency standards for passenger cars. Peters added that the Bush plan calls for automakers to improve fuel economy by 4 percent a year beginning in 2010 for passenger cars and 4 percent a year for trucks and SUVs beginning in 2012. While attending the Washington Auto Show on Wednesday, House Speaker Nancy Pelosi expressed optimism that Congress and the Bush administration could work out their differences.