Comment on missemme's post
That might work if he is really clueless. If he's just a selfish lover, you have to threaten him with going to s.o. else. If he's using withholding good sex as a passive-aggressive weapon, you have to find out what his beef is and resolve it.
Comment on smoothy's post
Telling your partner what you propose to do if he keeps stonewalling is not a push and shove match. It is a fair and honest communication of what the consequences will be if he continues to refuse to communicate and compromise and meet you halfway. Allowing people to be selfish and engage in dysfunctional behavior without consequences doesn't help anyone.
At the same time, it is true that you owe him honest and open communication, and fair and balanced negotiation. So as you say, cheating (i.e. going behind his back for sex) is not an option. That is, however, totally different from telling him that you you want an open relationship if he can't compromise with you to both your satisfaction on your sexual needs. It's an honest way of solving a sexual incompatibility problem without resorting to divorce. Open relationships are not cheating, because all parties to them have to agree to them as the best solution to make the relationship work.