Asia Tech Wire (Sep 19) -- Apple is about to receive a warning from the European Union to open up its highly secretive iPhone operating system to be compatible with rival technologies or face a hefty fine, according to Bloomberg.

Citing people familiar with the matter, the report said that EU regulators will announce under the EU's Digital Markets Act that Apple will have to comply with strict new rules to make the operating system fully compatible with other technologies.

One of the EU regulators' goals is to ensure that other developers have access to key iPhone features, such as Siri voice commands and payment chips.

If Apple fails to comply, the EU may decide to launch a formal investigation, which could ultimately lead to a hefty fine of up to 10% of annual global turnover.