Wiedeking told the newspaper that European Union plans to require that emissions be cut to an average of 130 grams per kilometer for all new cars from 2012 were "completely naive."

French counterpart Christian Streiff, head of PSA Peugeot Citroen, was quoted by Hangelsblatt as calling the EU limits "totally unrealistic."

The German luxury sports car maker and the French auto giant have decided to join forces with others to oppose the plan.

The head of Germany's automobile federation VDA, Matthias Wissman, was quoted as saying: "We have reached an agreement within the framework of the ACEA" or European Automobile Manufacturers' Association.

Wiedeking told Handelsblatt that current models of Porshe's popular luxury cars would not meet the limits and that the EU should set separate standards for each of the market's segments.

EU proposals requiring emissions to be cut sharply by 2010 were "physically" not possible for Porsche sports cars to adhere to, Wiedeking said.

"Realistically, emissions requirements can only be graded by vehicle segment," Wiedeking told the newspaper.

Common regulation of emissions would undermine innovation in the automotive industry moreover, because the premium car segment would be eliminated from the market in favor of compact car makers, he added.

"A common limit for everyone is a business generation plan for compact car makers," Wiedeking said.

But Handelsblatt noted that details of the joint action remained to be hammered out.

German automakers, many of whom produce mainly large, powerful cars, mainly want to see separate standards set for the various market segments, while those in Italy and France, which turn out more smaller cars, are happy with a single standard for all vehicles.

Carbon dioxide emissions standards are easier to meet with smaller engines.

The German group DaimlerChrysler has also blasted the plan, but EU officials have nontheless threatened European automakers with sanctions if they fail to meet the proposed new regulations.

"If auto manufacturers do not fulfill their obligations, there will be appropriate sanctions," European Environment Commissioner Stavros Dimas told the Sunday newspaper Bild am Sonntag.

Earlier this month, German Environment Minister Sigmar Gabriel also spoke out on the issue, threatening automakers with fines if they did not respect the new EU standards.

A first draft of the new rules is expected to be ready in the first half of 2008.

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