Answering a question, especially in a public forum, is a tricky thing that not everyone can master. Especially when you are in a sort of communication role where you are representing a large entity (like the United States government), every single word you say has to be measured.
So it’s probably a good idea to think before you talk – but then, you don’t want to spend too long thinking otherwise you’ll be standing with a blank stare on your face with scores of people waiting to hear your reply.