Germany outlines laws on reducing CO2 emissions

Europe's largest economy invests 120 million euros a year on climate protection, he added, and will double the proportion of renewables in national power output to 25 percent.

Germany's CO2 reduction has stagnated since the mid-90s. Gabriel acknowledged over half of its 18 percent cut since 1990 is due to the collapse of the heavily polluting Communist East German industry that disappeared after unification.

Gabriel said because much of the emissions reductions had been reached in this way, Germany's target for an additional 20 percent cut by 2020 was therefore ambitious.

"Let's just say, it's going to be much harder to achieve this target for the second half, than it was achieving the first (20 percent)," he said.

Greenpeace has criticized the government for supporting the construction of some 20 coal-burning power plants, needed to fill the void created by the phasing out of nuclear power.

The environmental group has said that if all 24 planned power plants are built -- six are under construction -- there is no way the country can meet its target of cutting CO2 by 40 percent.

(Reporting by Sylvia Westall)