The move against the US giant marks the latest attempt by the 27-nation EU to rein in Big Tech, in the face of strong pushback by the government of US President Donald Trump.

The probe falls under the bloc's antitrust rules rather than its newly reinforced digital laws, which Trump has accused of unfairly targeting American firms -- threatening retaliation.

The European Commission said it was concerned that a newly announced Meta policy "may prevent third party AI providers from offering their services through WhatsApp".

WhatsApp pushed back against the claims as "baseless".

But EU competition chief Teresa Ribera said the bloc must "act to prevent dominant digital incumbents from abusing their power to crowd out innovative competitors".

"This is why we are investigating if Meta's new policy might be illegal under competition rules, and whether we should act quickly to prevent any possible irreparable harm to competition in the AI space," Ribera said in a statement.

The EU says the Meta policy announced in October will bar rival AI providers from using a tool in the business version of WhatsApp to reach customers directly.

The restriction applies "when AI is the primary service offered" -- as with an AI chatbot or assistant -- though firms may still use AI tools for support functions such as customer support.

"As a result of the new policy, competing AI providers may be blocked from reaching their customers through WhatsApp," the commission said.

"On the other hand, Meta's own AI service 'Meta AI' would remain accessible to users on the platform."

WhatsApp rejected the argument that it risked hindering competition.

"The claims are baseless," a spokesperson said. "The emergence of AI chatbots on our Business API puts a strain on our systems that they were not designed to support."

"Even still, the AI space is highly competitive and people have access to the services of their choice in any number of ways, including app stores, search engines, email services, partnership integrations, and operating systems."

- Multiple cases -

The EU probe covers the European Economic Area, made up of the bloc's 27 states, Iceland, Liechtenstein and Norway -- with the exception of Italy, which opened a separate investigation into Meta in July.

The Italian antitrust body has said that by merging Meta AI with WhatsApp the US giant may be imposing the use of its AI services on users and channelling its customer base into the emerging market.

There is no legal deadline for concluding an antitrust investigation.

Meta already faces the risk of heavy fines under the bloc's Digital Services Act (DSA), which regulates content.

One DSA case accuses Meta of failing to grant researchers sufficient access to public data, another focuses on accusations Meta platforms Facebook and Instagram do not provide user-friendly ways to flag illegal content or challenge content-moderation decisions.

EU regulators are also investigating Facebook and Instagram over fears they are not doing enough to combat the addictive nature of their platforms for children.

Meta has separately appealed against a 200-million-euro fine imposed this year under the bloc's Digital Markets Act competition law over its policy asking users to choose between an ad-free subscription and a free, ad-supported service.

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