President Donald Trump has threatened to hit the European Union with “substantial” new tariffs following the bloc’s decision to slap Google with more than $1 billion in fines for alleged anti-competitive practices.

In a series of posts on Truth Social on Friday, Trump accused European regulators of “robbing” American companies and the U.S. taxpayer. He pledged to immediately launch a Section 301 trade investigation into the EU’s actions, signaling a potential breach in delicate transatlantic trade relations.

“The European Union will pay a very big price for this illegal and highly unethical conduct,” Trump wrote, adding that he anticipates placing a substantial tariff on the 27-nation bloc at the “earliest possible moment.” He further declared that the U.S. is “not a ‘PIGGYBANK’ for Europe.”

The friction follows the European Commission’s penalization of Google for allegedly favoring its own services on Google Search and restricting consumer choices on Google Play. While Trump claimed the fine was issued “without explanation,” EU regulators had released detailed documentation outlining the antitrust violations.

The president’s escalation comes just one day after U.S. Trade Representative Jamieson Greer cautioned that actions against U.S. tech firms could strain bilateral ties. Trump has consistently defended American tech giants, whose leaders — including Google CEO Sundar Pichai, Tesla Inc. CEO Elon Musk, and Meta Platforms Inc. CEO Mark Zuckerberg — have cultivated close ties with his administration. Google contributed $1 million to Trump’s 2025 inaugural fund, and Pichai previously praised the White House’s leadership on artificial intelligence (AI) policy during a private executive dinner last fall.

The sudden threat endangers the fragile Turnberry deal struck last fall between Trump and European Commission President Ursula von der Leyen, which capped U.S. tariffs on EU exports at 15%. European officials had initially expressed relief on Friday when a separate round of U.S. tariffs, focused on supply-chain labor practices, maintained a 10% rate for the EU, honoring the agreement.

However, Trump’s latest economic warning has sparked immediate concern across the Atlantic. Bernd Lange, chair of the European Parliament’s Committee on International Trade, warned that executing the threat would unravel the Turnberry pact and provoke a severe counter-response.

“This reaction is destabilizing precisely the level of cautious security that had been achieved through intensive negotiations,” Lange said, noting the threat represents a direct attempt to exert political influence through trade policy.

Lange indicated that such moves could trigger Brussels’ Anti-Coercion Instrument — often referred to as the EU’s “trade bazooka” — which empowers the bloc to retaliate with targeted tariffs and countermeasures of its own.

While the European Commission declined to comment beyond its previous statements regarding the Google ruling, European lawmakers are watching closely to see if the Office of the U.S. Trade Representative formally initiates the probe. The USTR is already pursuing several high-stakes trade investigations, including a broad probe into global manufacturing capacity and a Section 301 inquiry targeting German pharmaceutical pricing.