Delete team project from Visual Studio Team Services

I am using Team Services on domain visualstudio.com and I need to delete one project, I found out that I need to use command prompt to delete projects, but when I tried the script it seemed that it doesn't work

My Script is,

TfsDeleteProject 
  /force collection:https://mytfs.visualstudio.com/DefaultCollection MyProject

My first mistake was that I didn't append DefaultCollection to the URL, but now I get error that I don't have privileges.

Thanks to @Christopher I was able to make the script work.

You can use the following command from the "Developer Command Prompt":

TfsDeleteProject /collection:https://mytfs.visualstudio.com/DefaultCollection MyProject