Google has sent a cease and disist letter to Microsoft for building a native YouTube app for Windows Phone 8, and violating its terms of service in three areas.

In the letter, Google explains, “It appears that the application: (1) allows users to download videos from YouTube; (2) prevents the display of advertisements in YouTube video playbacks; and (3) plays videos that our partners have restricted from playback on certain platforms (e.g. mobile devices with limited feature sets). These features directly harm our content creators and clearly violate our Terms of Service.”

Here’s the letter in its entirety (via The Verge):

Microsoft has responded to the situation. The Verge quotes a spokesperson as saying: “We’d be more than happy to include advertising but need Google to provide us access to the necessary APIs. In light of Larry Page’s comments today calling for more interoperability and less negativity, we look forward to solving this matter together for our mutual customers.”

You can hear Page’s comments near the end of the Google I/O keynote here.

Google has so far given Microsoft until May 22nd to remove the app. It launched last week.