Offer arrived, can I still ask for more? after 4 years as an administrative assistant

I want to negotiate but I am afraid they will withdraw. I am in Denver, in case local advice matters. The hiring manager was friendly and open. What wording worked?

Most employers expect a short conversation. Mine did not even blink.

I thanked them and said I was excited but hoped we could talk about the pay. They came back with a bit more.