The World Trade Organization agreed on Tuesday to investigate whether the United States has withdrawn billions of dollars of subsidies to airplane manufacturer Boeing, in response to a request by the European Union. The WTO also said it would arbitrate an EU request for countermeasures against the US totalling $12 billion (9.2 billion euros) a year. The development followed US notification to the Geneva-based trade arbiter in September that it had withdrawn aid to its large civil aircraft industry, in accordance with a WTO ruling made on March 23, 2012. Under WTO rules, member countries cannot fight these rulings made on appeal and must apply them. But the EU insists that the US has not complied fully with the ruling. As a result, the EU made a request on October 11 for a panel of WTO experts to investigate if the US was in compliance. The countermeasures requested by the EU were consistent with the \"unprecedented amount of subsidisation\" of US aircraft, the EU maintained, according to a source close to the WTO. For its part, the US did not object to the EU request for arbitration at the WTO, although it baulked at the level of proposed sanctions and to the imposition of a \"facilitator\" to gather information concerning the \"serious prejudice\" caused by the subsidies.