Google implied Wednesday that it may no longer be able to offer the Android operating system to device manufacturers for free, following a $5 billion antitrust fine from the European Union.

"So far, the Android business model has meant that we haven't had to charge phone makers for our technology," Google CEO Sundar Punchai said in a statement. "But we are concerned that today’s decision will upset the careful balance that we have struck with Android, and that it sends a troubling signal in favor of proprietary systems over open platforms."

Device makers are able to use and modify the open-source Android operating system on their devices for free.

The E.U. said Wednesday that Google violated antitrust rules by requiring Android device makers to bundle its apps like Chrome and Gmail, which harms competition.

The E.U. fined the Alphabet-owned company $5.05 billion, and threatened additional fines of up to 5 percent of Alphabet's daily global business if it does not end its bundling practices.

Pichai said that some of the apps pre-installed on Android devices generate revenue for the company, but also argued that they all "help ensure the phone ‘just works’, right out of the box." The statement also says that the pre-installed apps are easy to remove and replace with alternatives from outside developers.

However, the E.U. claims that the bundling practice is a particularly big problem because of Android's dominance among mobile operating systems. The ruling says that, excluding China, Android accounts for 95 percent of the market.

"Market dominance is, as such, not illegal under E.U. antitrust rules," the ruling states. "However, dominant companies have a special responsibility not to abuse their powerful market position by restricting competition, either in the market where they are dominant or in separate markets."

Pichai said Google will appeal the decision.