Personally, I would not be standing back, holding the leash. I wouldhave my hands in the dog's collar, to yank back hard in case of the dog behaving threateningly to the rabbit.
I would probably place the rabbit on eye level with the dog, rather than on the floor. This would limit the dogs ability to use its paws on the bunny.
I would have someone very close to the bunny, and someone in firm control of the dog.
Remember, the nature of the dog's breed will have some degree of influence on its behaviour. If it is a variety Staffordshire Terrier, remember that these dogs were originally bred for sporting purposes (eg. dog fights, etc.), and thus have some level of aggression towards other dogs, which may be extended towards the rabbit.
As it is a puppy, it is not possible to have a complete sense of its temperment. Proceed very carefully. Read up on this throughly.
All you need is one grab and shake = dead rabbit
* Do not just throw them in the same room together. Stupid, deadly idea.