How soon before you try and/or ask for sex in a new relationship ?

Is it a dealbreaker if the attempt to get or the request for sex is fobbed off or just outright denied?

Have you ever been the receipient of such an attempt or request and elected to say no instead of 'caving' to the 'peer pressure' so-to-speak of the moment? How did that go down? Was that the end of the relationship?