Both sides have threatened tariffs after the Geneva body found neither adhered fully to its findings. However, the United States has a head start, with the European Union having to wait until early in 2020 to hear what level of retaliation it can exact over Boeing. The WTO is expected this week to reveal the amount of EU goods the United States can target. People familiar with the case say the three-person tribunal is expected to award it around $7.5 billion, a record for the 24-year-old watchdog.
Such retaliation rights are rarely granted by the WTO - most parties reach settlements - and in many cases complainants do not exercise their rights. The United States though has indicated it will target EU goods to the fullest extent. It has already published a $25 billion list from which it will pick items to target from aircraft and aerospace parts to wine, cheese and luxury goods.
The WTO award in the world's largest corporate trade dispute could fuel already strained trade tensions, diplomats say. EU manufacturers are already facing US tariffs on steel and aluminium and a threat from US President Donald Trump to penalise EU cars and car parts. The EU has in turn retaliated.
Trade talks between the two, designed to ease tensions and ward off the threat of a tit-for-tat tariff war, have not gone well. The two sides have made some progress on regulatory cooperation, but a proposed deal to reduce duties is stuck, with Washington saying agriculture should be included and Brussels insisting it cannot.
The Trump administration has concluded that tariffs were effective in bringing China to the negotiating table over trade, and in convincing Japan to open its agricultural market to US products. Washington is unlikely to skip the opportunity to implement tariffs in the case over aircraft subsidies, according to current and former US officials.
Airbus has said this would lead to a 'lose-lose' trade war. Some US airlines have urged the administration not to go ahead with the tariffs, saying they could lead to layoffs. The parties could still theoretically resolve the issue and stave off sanctions, but both sides accuse the other of failing to respond to invitations to reach a negotiated settlement.
US officials say the decision about next steps will be up to US President Trump. The EU cannot retaliate immediately to any tariffs as it did following the US imposition of metal tariffs in 2018. It can either wait until a pronouncement in the parallel Boeing case or possibly revive an existing right to hit $4 billion of US imports in a WTO dispute over US tax breaks for exports, even though the two sides settled in 2006. Such a move would likely be strongly contested by Washington.