The European Commission, the EU's executive body, had proposed capping carbon dioxide emissions from new cars to an average of 130 grams per kilometer by 2012, compared with a current EU average of 158g.

Other improvements such as better tires, gears and air conditioning are hoped to take the level down to 120g.

The move is part of a broader EU effort to cut CO2 emissions by at least a fifth by 2020, compared with 1990 levels, in a bid to stave off the worst effects of climate change.

But the Liberal and Conservative groups in the European Parliament's influential industry committee have agreed to propose phasing in the 130g target to 2015, one lawmaker said on Monday on condition of anonymity, because negotiations on other elements of the package are still underway.

Whether the phase-in between 2012 and 2015 has majority backing from members of the committee will only be seen after voting late on Monday.

The proposal would then still have to be accepted by the overall parliament and EU member states before becoming law.

Environmental campaigning group Greenpeace says such a phase-in would mean CO2 emissions would only be cut by 8g to around 150g by 2012, which it said was another example of lawmakers watering down legislation aimed at protecting the environment.

But German Conservative lawmaker Werner Langen, who is leading the legislation through the industry committee, said a phase-in was fair and realistic.

"If we can get such a solution underway, the EU will have a practical piece of legislation which could serve as a model for other regions in the world," he said.

The European Commission has also proposed a long-term target of cutting CO2 emissions from new cars to 95g by 2020 and the Liberal and Conservative groups were still discussing whether that goal should be made binding or not, added the lawmaker.