The European Union’s executive arm has started a process to provide Apple with guidance on how the iPhone maker can comply with rules to ensure its operating systems are functional with other technologies.

Apple Inc. has been warned by the European Union to open up its highly guarded iPhone and iPad operating systems to rival technologies, or eventually risk significant fines under its flagship digital antitrust rules.

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 on Thursday launched proceedings to ensure that Apple complies with landmark rules requiring it to open up its closed ecosystem to rivals. Under the so-called specification proceedings,