BERLIN -- German environmentalists hope the country's stewardship of the Group of Eight and the European Union in 2007 will help steer the car-crazy nation towards imposing speed limits on its unrestricted autobahns.

They say that if motorists took their foot off the throttle a little, this would cut greenhouse gas emissions and help Germany brush up its green credentials.

"In the past few years, the reduction of greenhouse gases has stalled even in our country," Andreas Troge, president of the German Federal Environment Agency and a government environment adviser, was quoted on Thursday as telling the newspaper Berliner Zeitung.

A limit of 120 kilometers per hour (75 mph) would reduce carbon dioxide emissions -- one of the so-called greenhouse gases that contribute to global warming -- by about 30 percent, Troge said.

His suggestions, which echo past calls for speed restrictions to reduce road deaths, were welcomed by the Greens and other environmental groups.

However, Germany's transport minister rejected the idea.

"I am committed to a reduction in emissions but a general speed limit on open stretches of road does not make sense," minister Wolfgang Tiefensee said in a statement.

About one-third of Germany's highways already have a speed limit while the rest carry a recommended speed of 130 kph (80 mph). In reality, drivers and motorcyclists can, and often do, travel as fast as they like.

Home to high performance car makers such as BMW, Mercedes-Benz and Porsche, as well as mass market producers Volkswagen and General Motors' Opel division, Germany has resisted speed limits.

The car lobby argues that roads free of limits encourage manufacturers to develop safer cars, thus securing jobs.

"With its demands for a speed limit, the Environment Agency is just attempting to reheat a discussion which came to an end ages ago," the ACE motorists' association said in a statement.

The Financial Times Deutschland was clear in a commentary on its Web site: "Derestricted driving on the autobahn is to the Germans what pesto is to the Italians and the baguette is to the French. No one in Italy or in France would dare to try and ban the cultural characteristics of their country."