BRUSSELS - U.S. chipmaker Intel's fight against a 1.06 billion euro ($1.2 billion) EU antitrust fine was boosted on Thursday by an adviser to Europe's top court finding EU regulators at fault on their economic analysis.

The case dates from 2009 when the European Commission fined Intel for trying to thwart rival Advanced Micro Devices by giving rebates to computer makers Dell, Hewlett-Packard Co, NEC and Lenovo for buying most of their chips from Intel.

Regulators generally oppose rebates offered by dominant companies on concerns they may be anti-competitive, while companies in turn say enforcers must prove that discounts are anti-competitive effects before sanctioning them.

A lower tribunal had in 2022 scrapped the fine, prompting the EU competition enforcer to appeal to the Luxembourg-based Court of Justice of the European Union (CJEU).

CJEU Advocate General Laila Medina, who only focused on two of the six grounds of appeal, said judges should dismiss both of those grounds.

"The court should confirm that the Commission erred in applying the AEC test with respect to HP and Lenovo," she said in a non-binding opinion.

The AEC test assesses to what extent equally efficient competitors can still compete despite rebates offered by the dominant company.

The CJEU, which will rule in the coming months, follows the majority of such recommendations.

The Commission last year re-opened the case and handed out a 376-million-euro fine to Intel, citing illegal payments made by the company between November 2002 and December 2006 to HP, Acer and Lenovo to halt or delay rival products.

The case is C-240/22 P Commission v Intel Corporation.

(Reporting by Foo Yun Chee; Editing by David Goodman and Hugh Lawson)