iframe allow vertical scrollbar but not horizontal

I have an HTML iframe. I want it to be scrollab开发者_StackOverflowle vertically, but not horizontally. Is this possible?

Automatically shows vertical scrollbar if content is longer than viewable area:

.iframe-class { overflow-x:hidden; overflow-y:auto; }

Forces vertical scrollbar even if content is not longer than viewable area:

.iframe-class { overflow-x:hidden; overflow-y:scroll; }