The European Union threatened on Wednesday to retaliate if the US proceeds with slapping tariffs on $7.5 billion worth EU goods.
"If the US decides to impose WTO authorised countermeasures, it will be pushing the EU into a situation where we will have no other option than do the same," the EU said in a statement.
Earlier in the day, the World Trade Organisation (WTO) approved US tariffs on $7.5 billion of EU goods over illegal subsidies for Airbus.
The trade dispute between the two major airframe makers began in 2004 when Washington accused the UK, France, Germany and Spain of providing illegal subsidies and grants to Airbus.
In 2005, the EU fired back, observing that Boeing had received $19.1 of prohibited subsidies from the US government between 1989-2006, according to France24.
Earlier this year, the WTO ruled that the US had failed to remove all of its prohibited subsidies.