GENEVA (Reuters) - A European Union trade lawyer fired withering put-downs at U.S. claims for damages due to subsidies for European planemaker Airbus in a recording of a dispute hearing made available by the World Trade Organization (WTO) on Tuesday.

FILE PHOTO: A logo is pictured outside the World Trade Organization (WTO) headquarters next to a red traffic light in Geneva, Switzerland, October 2, 2018. REUTERS/Denis Balibouse

The EU lawyer, whom diplomats identified as James Flett, described some U.S. claims in the case as “frankly childish” and said some of the data appeared to have been provided by Airbus’ U.S. rival Boeing Co.

The two firms’ rival claims have fueled almost 15 years of litigation at the WTO. After both were found to have received illegal subsidies, each side wants to gain the upper hand by winning the right to trade sanctions to compensate for economic damage.

The latest comments, released as an audio recording on Tuesday, were made at a dispute hearing in February. Hearings are normally secret, but a few are made public.

An unnamed U.S. trade lawyer spoke first for about 30 minutes, saying the U.S. calculation was “eminently straightforward and logical”, amounting to an annual $10.8 billion in damages.

Denying such a level of sanctions would “cement in perpetuity” the damage done by the EU subsidies, which had caused the United States “economic pain” for at least two decades, he said.

After 14 years of litigation it was long past time for the EU to argue about the damage it had done.

“The EU is wrong,” the U.S. lawyer told the hearing.

U.S. President Donald Trump tweeted about the dispute on April 9, promising $11 billion of tariffs.

“The EU has taken advantage of the U.S. on trade for many years. It will soon stop!,” Trump wrote.

In a statement that ran to 100 minutes, Flett accused the United States of using double counting and unreliable data to inflate the amount of damage caused by Airbus subsidies and to erroneously claim that the damage was recurring.

In fact, the continuing effect of the subsidies was “precisely zero”, Flett said, describing it as “an inconvenient truth”.

Substantial parts of the evidence required to support the U.S. case were “missing, incomplete, inconsistent, non-verifiable, and in fact, wholly unreliable”, he added.

The U.S. case included price data for Boeing planes, but it was distorted because the prices mainly related to VIP customers, he said.

“This is really serious, Mr. Chairman, because at the moment, what you’re looking at is numbers, apparently, that have been provided by Boeing. Boeing has a massive commercial interest in the outcome of this process,” he added.