1) Give us some time to think about it.
2) We are going to re-focus the discussion on a different compensation lever where we can present something you're already going to get as if it were a new incentive justifying your concession on a lever you're currently interested in.
You can do both of these as a job seeker.
(For example, if you have extra-curricular interests like many desirable tech employees do, the extra-curricular interests can be used to justify an increase in your compensation vis-a-vis a hypothetical employee who punches out of the Internet at 5 pm. It doesn't particularly matter that you're going to continue blogging and OSS regardless of the outcome of this negotiation, you just frame the discussion such that that becomes newly discovered value which gives the other party something to hang their hat on for getting you that last $10,000.)