The European Union plans to hit Alphabet Inc.’s Google with a record antitrust fine of €4.34 billion ($5.06 billion) on Wednesday, according to an official familiar with the matter, in a decision that could loosen the company’s grip on its biggest growth engine: mobile phones.

A formal decision — which would mark the EU’s sharpest rebuke yet to the power of a handful of tech giants — is set to be taken during Wednesday morning’s meeting of EU commissioners following a presentation by competition chief, Margrethe Vestager, according to the person. No discussion of the decision is expected, the official said.

The EU’s antitrust regulator has been looking into whether Google GOOG, -0.24% GOOGL, -0.01% had abused the dominance of its Android operating system, which runs more than 80% of the world’s smartphones, in order to promote and entrench its own mobile apps and services — particularly the company’s eponymous search engine.