The EU said Apple must make sure devices made by rivals work with its iPhones and iOS operating systems in accordance with the Digital Markets Act

EU antitrust regulators launched proceedings on Thursday to ensure that Apple complies with landmark rules requiring it to open up its closed ecosystem to rivals or risk a possible hefty fine.

EU authorities say Apple has failed to come into compliance with the Digital Markets Act, a newly enacted regulation aimed at large tech companies.

Apple said it has “created ways for apps in the European Union to request additional interoperability with iOS and iPadOS while protecting our users.”

The EU has told iPhone maker Apple to allow access to its tightly controlled iPhone and iPad operating systems to rival companies and third-party developers or possibly face anti-trust fines. The EU has given the Californian company a six-month deadline to resolve these issues.