BRUSSELS, March 11 (Reuters) - Airlines outside the European Union may be forced to pay duties to the EU if they use government subsidies to slash their ticket prices under plans the European Commission is expected to endorse on Tuesday. The plan could affect airlines in the United States -- and any other subsidised non-European price cutter -- but is not in any way a response to a U.S. decision to erect tariff barriers to steel imports, an EU official said. It is a response to subsidies granted to airlines following the attacks of September 11, when European airlines suddenly faced subsidised competition. Countries complained to the EU. "We were defenceless," said EU spokesman Gilles Gantelet. "We didn't have any legal tools to do anything." So the EU has proposed a provision similar to one that the U.S. has had since 2000. "This is simply closing a loophole," Gantelet, spokesman for EU Transport Commissioner Loyola de Palacio, told Reuters. The plan, which has to win approval from the European Parliament and the governments of the 15 member states, would impose measures similar to anti-dumping provisions used for goods such as steel and for maritime trade. The proposal is so uncontroversial at this point that the Commission has scheduled no debate on the matter and is expected to rubber stamp the plan unanimously. In fact, Gantelet said that there are no problems for the time being that would require use of the provision. "There are no problems currently with the Americans or the Swiss," he said. "We had had more problems in the past with the Swiss." Airlines could complain to the EU about unfair treatment or the Commission could initiate an action, Gantalet said. In either case there would be time for talks before the duties were imposed. "It's one thing to say 'please,'" he said. "It's another thing to say, 'If you don't stop this practice I will apply the regulation.'" An EU official expressed concern that without the measure, unfair competition by government-subsidised airlines could eventually drive some EU airlines out of business. "EU airlines are under strict rules and get no operating subsidies," the official said. "They have to struggle to survive." Belgian national airline Sabena declared bankruptcy in November after it was barred by EU rules from getting government help to bail it out.