LoadLevelAsync Wait to load (C#)

Hello, I'm trying to load a level using a loading screen and so far I've got a bit of it working. However I'd like the user to have to press a key before continuing to the actual level. This is what I have so far and in my mind it should work, but obviously its not :/

 IEnumerator LoadLevel()
     {
         AsyncOperation async = Application.LoadLevelAsync(levelName);
 
         while(!async.isDone)//This hits 90% and then loads level automatically
         {
             percent.text = (async.progress * 100).ToString("F0") + "%";
             yield return new WaitForEndOfFrame();
         }
 
         while(async.isDone)//This isn't working
         {
             percent.text = "Press Any Key to Continue";
 
             if(Input.anyKeyDown)
                 yield return async;
         }
     }