BEIJING - The China Air Transport Association has said it and its airline members do not acknowledge the European Union's Emissions Trading System (ETS), something they say would cost them billions of yuan each year.

"If the EU insists on carrying out the plan, the association will strongly recommend that the Chinese government takes even harsher counter-measures against flights in and out of China operated by airlines from EU member countries," the association said in a statement.

Experts said under international conventions concerning civil aviation, all sides are equal, and measures taken in one country or market cannot be implemented unilaterally. They noted the move by the EU to extend its ETS system to non-EU airlines without consultation violates such conventions.