The European Union says it will outline steps to compel Apple to open up its iPhone and iPad operating systems to competing technologies under the bloc’s tough new digital rulebook, which threatens hefty fines for breaches.

The European Union 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.

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EU watchdogs announced under the bloc’s Digital Markets Act that Apple must step into line and make operating systems fully functional with other technologies

While the announcement is a step shy of being a formal investigation, the EU aims to compel Apple to re-engineer its services to allow rival companies to access the iPhone’s and iPad operating systems.

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.