<human>: Can you condense the text into a few key points?

For some context; Today one of my friends asked me on a coffee date with them this weekend. Having never been asked out before, it took my by such surprise that I said "errrm yeah sure" and regretted it immediately afterwards.

I was wondering what I do now, knowing that I don't want to go on a date with them this weekend? 

I didn't want to say "oh wait, actually, no I don't want to" after already saying "yes" since I thought it would be a pretty horrible thing to do, and know I would have been crushed if that had happened to me. At the same time, I don't want to lead them on and let them think I might feel the same way when I don't. 

I feel even worse as I am actually looking for a girlfriend right now, I just don't want it to be her (as harsh as that sounds). Don't get me wrong it is flattering, I just don't feel the same way.

Does anyone have any advice for this situation?

I thought of maybe saying something to them tomorrow along the lines of "at the time I thought you meant as friend, but then I realised you might have meant as a date and, sorry, but I don't feel the same way" or something like that, but I can't decided if that is a horrible idea or not...
<bot>: Said yes to my friend asking me out in panic, but I don't want to go on a date with her. How do I let her know/let her down gently?