European competition commissioner Margrethe Vestager is expected to announce a fine Wednesday | John Thys/AFP via Getty Images Google faces multibillion euro fine in Android antitrust decision Margrethe Vestager is expected to charge Google over unfairly using its popular mobile software to maintain its dominance in search.

Google is in the crosshairs of Europe's antitrust enforcers — again.

The tech company is expected on Wednesday to be fined billions of euros and to be forced to change some of its business practices related to Android, its popular mobile operating system, according to three people with direct knowledge of the matter.

The official ruling — expected around midday in Brussels on Wednesday — by Margrethe Vestager, Europe's competition czar, marks the latest antitrust tussle between Brussels and the tech giant. Google already faces two other competition charges that it favors some of its search services over those of rivals and that some of its advertising products restrict consumer choice. The company denies wrongdoing in all three cases.

The size of the financial penalty against Google is expected to exceed a separate antitrust fine of €2.4 billion ($2.8 billion) last year against the search giant, according one of the people who spoke on the condition of anonymity. It would represent Europe's largest financial penalty ever levied against a single company.

The decision will ratchet up the pressure between Brussels and some of Silicon Valley's biggest names after Microsoft, Google and Intel, collectively, were already hit with nearly €6 billion ($7 billion) in antitrust fines over the last decade, excluding Wednesday's expected levy. The Commission also has demanded that Apple repay €13 billion ($15 billion) in back taxes to the Irish government, a ruling that both Dublin and the iPhone maker are appealing.

Vestager — whom U.S. President Donald Trump reportedly called Europe's "tax lady" — insists that she is not picking on U.S. tech companies. But her critics will likely view the latest multibillion euro fine as a fresh European attempt to rein in U.S. economic dominance by targeting some of its largest companies — rhetoric that will only raise the intensity of an ongoing trade war between Brussels and Washington.

By focusing on Android — mobile software that powers more than three-quarters of the region's smartphones, according to industry estimates — Europe's competition chief is raising the stakes in her fight with Google, targeting software that lies at the core of its future business plans in a world where mobile devices are increasingly taking over from desktop computers.

"Google has a lot of market power," said Harry First, co-director of the competition, innovation, and information law program at New York University. "It's a scary situation, it's an absolute nightmare."

Spokespeople for the Commission and Google declined to comment on the upcoming antitrust announcement.

Vestager's antitrust decision will likely claim that Google uses Android and its other mobile services to maintain its dominance in online search at the expense of rivals.

The ruling is expected to focus on complex contractual agreements that Google uses to promote its search service and Chrome browser. As part of these deals, the search giant requires manufacturers to pre-install and set these services as default if they want access to the company's popular app store, known as Google Play.

Such contracts hamper the rise of rival mobile operating systems and digital services, reduce competition in online search and stifle the wider digital market for consumers, according to EU officials.

"We believe that Google's behavior denies consumers a wider choice of mobile apps and services and stands in the way of innovation by other players," Vestager said when she announced the charges last year.

The Android decision will represent only the beginning of a lengthy legal battle that may eventually be appealed in Europe's highest court. Google may have up to 90 days to provide the Commission with proposed remedies to its alleged anticompetitive behavior, though its rivals are expected to fight tooth and nail to open up the mobile software to greater competition.

Google has defended its use of Android, saying that there is significant competition in the smartphone industry and that its open-source mobile software has driven down prices for devices and created thousands of app-developer jobs.

"Android is not a one way street; it’s a multi-lane highway of choice," Kent Walker, the company's general counsel, wrote in a blog post in late 2016.