The United States confirmed on Friday it has received a confidential World Trade Organization ruling in its multibillion-dollar complaint against European government support for Airbus .

We are still reviewing the interim report, which is over 1,000 pages long. Because the interim report is confidential, we cannot discuss the contents, said Debbie Mesloh, a spokeswoman for the U.S. Trade Representative's office.

The United States has always maintained that the European governments have provided unfair subsidies to Airbus that harm U.S. interest, Mesloh added, alluding to Airbus' U.S. rival Boeing , which pressed USTR to bring the case.

In this dispute, the United States is challenging dozens of measures providing over billions of dollars in subsidies to Airbus, including launch aid to every major Airbus aircraft model, she added.

Since the United States brought the case in 2004, the governments of France, Germany, Spain and Britain have continued to provide contested launch aid loans for Airbus.

The European aircraft manufacturer's latest project is the A350 wide-body jet. Boeing officials have said they hoped Friday's confidential decision would halt some $4 billion in European launch aid loans for that aircraft.

The dispute has proven to be one of the most complex and lengthy disputes under the WTO, Mesloh said.

(Reporting by Doug Palmer; editing by Paul Simao)