Offer arrived, can I still ask for more? - 14 months and counting

I received an offer as a production planner and I think the pay is a little low. I have a competing interview next week. What wording worked?

If they say no, consider asking for something else, such as a review in six months.

Thanks for writing this out. I went through something close to it last year, and it got easier once I kept a simple log of every call and form.