BRUSSELS (Reuters) -Apple on Wednesday hit out at Meta Platforms, saying its numerous requests to access the iPhone maker's software tools for its devices could impact users' privacy and security, underscoring the intense rivalry between the two tech giants.

Under the European Union's landmark Digital Markets Act that took effect last year, Apple must allow rivals and app developers to inter-operate with its own services or risk a fine of as much as 10% of its global annual turnover.

Meta has made 15 interoperability requests thus far, more than any other company, for potentially far-reaching access to Apple's technology stack, the latter said in a report.

"In many cases, Meta is seeking to alter functionality in a way that raises concerns about the privacy and security of users, and that appears to be completely unrelated to the actual use of Meta external devices, such as Meta smart glasses and Meta Quests," Apple said.

Meta Quest is Meta's virtual reality headset, part of the company's ambition to own the computational platform that powers virtual reality (VR) and mixed reality (MR) devices.

"If Apple were to have to grant all of these requests, Facebook, Instagram, and WhatsApp could enable Meta to read on a user's device all of their messages and emails, see every phone call they make or receive, track every app that they use, scan all of their photos, look at their files and calendar events, log all of their passwords, and more," Apple said.

It pointed to Meta's privacy fines in Europe in recent years as a cause of concern.

"What Apple is actually saying is they don't believe in interoperability," a Meta spokesperson said in a statement.

"Every time Apple is called out for its anticompetitive behavior, they defend themselves on privacy grounds that have no basis in reality."

Separately, the European Commission - which in September said it would spell out how Apple must open up to rivals - published its preliminary findings on the issue late Wednesday evening, giving individuals, companies and organisations until Jan. 9 to provide feedback on its proposed measures for Apple.

The measures would require Apple to provide a clear description of the different phases, deadlines and the criteria and considerations that it would apply or consider in assessing interoperability requests from apps developers.

Apple should also provide developers regular updates and give and receive feedback regarding the effectiveness of its proposed interoperability solution while there would be a fair and impartial conciliation mechanism to address technical disagreement with Apple.

The Commission also set out the steps for Apple to provide interoperability with all functionalities of the iOS notifications feature available to Apple Watch, Apple Vision Pro and any future Apple connected physical devices to its rivals as well.

A decision by the EU executive, which acts as the competition watchdog in the 27-country bloc, on whether Apple complies with the DMA's interoperability provision is expected in March next year.