Have you tried? I have to admit I've never tried it in GC3. I think I did in GC2 but I don't recall it ever working. I don't think I ever posed enough of a threat when I did.

Go to the communications screen, click "talk about something else", the option is there.

Hmmm, not there.  Must be a tech or gov type I need to have.  Playing Korath.  See options for expressing friendship, asking for or offering aid.  Anyway, will figure it out.

I have done it before and they mainly just give you money. If you do not see the option, wait until your power rating is much higher than the race from which you are demanding tribute and then try again.