The EU cautioned German auto giant Daimler Friday it must upgrade the air conditioning coolant used in its new models to meet greenhouse gas emission targets if they are to be cleared for sale.

"If Daimler does not meet this requirement, its new models cannot be approved," the office of European Union Industry Commissioner Antonio Tajani said.

New rules require EU automakers to use a new, less environmentally harmful gas in their air conditioning systems so as to curb greenhouse gas emissions, widely blamed for contributing to global warming.

"The European Commission must ensure that this legislation is respected," Tadani spokesman Carlo Corraza told AFP.

"It is not the European Commission which chose the new gas, it is the industry which decided on it after testing," Corraza said.

The new gas was tested extensively and approved by the German Automakers Association, VDA, of which Daimler is a member.

Daimler argued, however, that when it came to adapting its new models, it ran into problems with the new coolant which proved highly inflammable in certain cases. Accordingly it asked for an extra six months to meet the new standard.

Corraza said the Commission had "noted the request" but reiterated that all new auto models sold in the EU from January 1 onwards had to use the new coolant.

"The German authorities are tasked with testing vehicles and those that do not meet the new rules ought not to be registered," he added.