Delete a Test Plan in VSTS / Test Manager

Is there a way to delete a Test Plan in Visual Studio Team Services or through Microsoft Test Manager for a project hosted on Visual Studio Team Services?

Delete buttons seems to be disabled and directly deleting the work item in VSTS is blocked:

The work item 1 cannot be deleted. Test Plan work items cannot be deleted. work items cannot be deleted.

Any other way to achieve this?

As Abhijit mentioned, you need to use witadmin destroywi command to delete the test plan. This command works for VSTS too. But you need to make sure your account has "Team Foundation Administrators" permission. You can use this command directly from "Developer Command Prompt for VS" which is installed with VS.