Final Act of the movie

[M'Sharak]

^ It sounds familiar to me, too. That was quite a while ago, possibly even before primary shooting was wrapped.

Edit:

I think it might have been Romulans, though, instead of Klingons.

http://trekmovie.com/2008/05/16/star-trek-villain-spoilers/

Edit, again:

Aha, it seems he did talk about Klingons earlier:

http://trekmovie.com/2008/02/21/yelchin-chekov-is-no-kirk-or-spock/
http://trekmovie.com/2008/02/01/yelchin-sees-klingons/