Google's initial focus when it acquired Android back in 2005 was to beat Microsoft's early Windows Mobile efforts. (Photo:AP)

Google's triumph over Microsoft in the mobile business is irreversible and Bill Gates considers the missed opportunity as his biggest regret.

In a recent interview at Village Global, the Microsoft co-founder revealed that his greatest mistake ever was Microsoft missing the Android opportunity, CNET reported.

He said that his mismanagement "caused Microsoft not to be what Android is - a non-Apple phone platform."

Google's initial focus when it acquired Android back in 2005 was to beat Microsoft's early Windows Mobile efforts. Ultimately, Android suppressed Windows Mobile and Windows Phone.