The World Trade Organisation will rule shortly on the acrimonious dispute pitting US aviation giant Boeing against its European rival Airbus, one of the most complex to reach the international trade watchdog.

Boeing is confident it will win but some analysts say a clear-cut judgement is unlikely given the complexity of the case, which was brought by the US against the EU in October 2004.

They expect instead the wrangling over national subsidies for the aviation industry to drag on for several years before any firm resolution.

Washington charges that the EU illegally provides subsidies to Airbus, saying an accord that allowed Brussels to provide up to a third of development costs of new airliners was no longer valid since Airbus is now a major industry player and not the fledgling firm of when the deal was struck.

Washington estimates European state aid so far to be about €139 billion.

In turn, the EU laid a complaint with the WTO in the same year, accusing Washington of violating international trade rules by funnelling subsidies to civil aviation through military research funds.

Innovations from Boeing's military arm can be used by its commercial aircraft unit, Brussels argued, and therefore, research funding provided to Boeing's military unit was a form of subsidy.

Some $23 billion of subsidies were masked as defence research, Brussels claimed. If the damage to European aviation industry was calculated using the same figures as the US, it would amount to some $305 billion.

The WTO ruling expected this week deals with Washington's claim against Brussels and it is expected that it will not hand down a finding on the EU complaint for several months. "The expected report will only cover half the story. The other half is about market distorting US subsidies to Boeing. The draft interim report covering this is not expected for at least several months," Maggie Bergsma, spokeswoman for Airbus told AFP.

"We are years away from final rulings of the WTO and history shows the path ahead - years of pointless litigation will be followed by negotiations and finally a settlement," she added.