(REUTERS) — China will take swift counter-measures that could include impounding European aircraft if the EU punishes Chinese airlines for not complying with its scheme to curb carbon emissions, the China Air Transport Association said on Tuesday.

The warning came as the U.N.’s aviation body expressed concern about the growing threat of bilateral reprisals.

Chinese airlines, which have been told by Beijing not to comply with the European Union’s Emissions Trading Scheme, refused to meet a March 31 deadline for submitting carbon emissions data.