Can't delete certain files in Time Machine

I go into time machine wanting to delete some unwanted files and click on the grey gear at the top. However, when I do there is no option to delete the file, only to restore it. I'm operating on Mavericks and have been searching but have not yet found an answers. What is the problem and why can't I delete the file? With some of my more recent files I actually do have the option to delete them but this is not the case with files around 2 weeks old?