What do I do in this job-offering situation?

After a tedious interview process, I have finally received a job offer from an IT company. The new company in itself is in many ways better than my current employer, and I wouldn’t want to decline their offer; however the salary they are offering is just about the same (even a few bucks less) than I’m making at the current employer.
Shortly put, I would very much want to get the new job, however the money is just not enough!

My question is: how do I tell them that their offer is less than I’m making right now, and that i would gladly accept their offer, IF, they were willing to offer a higher salary?

Thank you :-)