Apple Inc. and Google’s Android were earmarked by the UK’s antitrust watchdog for a raft of new rules targeting their power in mobile ecosystems, a market almost completely dominated by the US giants.

Britain on Wednesday told Apple and Google to be fairer in how they distribute apps on their mobile platforms, setting out possible interventions as it plans to designate the U.S. tech companies with strategic market status over their duopoly.

"Around 90-100% of UK mobile devices running on Apple or Google's mobile platforms," the CMA said, adding this means the firms "hold an effective duopoly". Apple said it is concerned the ruling would negatively impact its customers in the UK, while Google called the decision "both disappointing and unwarranted".