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.

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.

The UK’s CMA will impose new rules on Apple and Google after designating them with strategic market status, aiming to boost app store competition and protect consumers.