The World Trade Organization is to issue a ruling Tuesday on a US complaint charging the European Union with illegal subsidies to aircraft manufacturer Airbus, an industry source said Friday.

"The decision will be made public on Tuesday afternoon," the source said, confirming another source close to the matter.

The six-year-old clash over subsidies, in which the EU has also lodged a complaint against Washington for what it claims is US support for Airbus rival Boeing, is one of the most complex trade disputes the WTO has dealt with.

The Geneva-based WTO confirmed last September that it had provided a confidential interim ruling on the dispute to the United States and the 27-nation EU but few details have filtered out.

The United States filed its WTO complaint in October 2004, triggering an immediate counter-suit by the EU.

US authorities contend that an accord allowing the EU to provide subsidies covering a third of the development costs of new Airbus airliners was no longer valid since Airbus is now a major industry player and not the fledgling firm when the deal was struck.

Boeing said recently it expected a ruling this month while the WTO has indicated that it should complete its work on the US complaint by April.

A first interim ruling in the EU complaint against the United States is due to be delivered in June, according to the WTO.