The EU will go ahead with its hotly contested plan to charge airlines for carbon emissions despite US threats of reprisal, should it win the backing of the European Court of Justice, EU sources said Tuesday. \"There\'s no question of giving up,\" an EU official told AFP on condition of anonymity. \"It\'s been approved by the European Union.\" The European court is to rule Wednesday on an EU decision to include from January 1 all airlines in its Emissions Trading System (ETS), which furious US, Canadian and other carriers say violates climate change and aviation pacts. As the deadline looms, US Secretary of State Hillary Clinton joined a mounting chorus of opposition with a warning of \"appropriate action.\" \"We strongly urge the EU and its member states ... to reconsider this current course,\" Clinton said in a letter sent to EU counterpart Catherine Ashton last week, that was obtained by AFP. \"Halt or, at a minimum, delay or suspend application of this directive,\" she said. \"Re-engage with the rest of the world.\" \"The United States stands ready to engage in such an effort. Absent such willingness on the part of the EU, we will be compelled to take appropriate action.\" The European Commission, the EU\'s executive arm, refused comment on the letter ahead of the decision by the Luxembourg-based court.