Conan O'Brien, NBC Settlement - One Final Thing

Conan O'Brien and NBC are one issue away from sealing a settlement deal -- and the ball is in Conan's court.

Conan has asked for $600,000 more in severance money for his staff. Sources tell TMZ NBC has told Conan's lawyers they will ante up something extra, but only if this is Conan's final demand.

As we first reported, NBC has already offered to pay Conan's staff a total $7.5 million. And his E.P. will rake in $4.5 mil himself and that's not part of the $7.5 mil.

A source close to the negotiations tells TMZ ... even if the network has to pay $600,000 more... it will still make money with the deal, considering they project they could be $45 million ahead if Conan leaves and Jay retakes the helm of "The Tonight Show" (because Jay would make $40 mil in a year and Conan is projected to lose $5 mil).

A network source says he expects it will all be a done deal tonight.