My suggestion would be not to rush the cat to get along.
I recently introduced Moby to my parent's hyperactive border collie mix. Younger dogs (and border collies) may have good intentions, but their play is too rough for a cat, and their approach is too happy (where cats are wary and approach with caution). I don't mean they will never be able to play, but the cat will need time to get used to the dog, and the dog needs to know he won't be able to play with the cat like he does with other dogs.
As long as the cat has places to hide/watch while the dog is around he will eventually get used to him. So I think it would be best not to hold the cat next to the dog - it might just freak him out and make him more scared. He/She'll have to observe for a while to realize the dog isn't a threat.
Moby progressed well over 4 days, but still preferred not to be right next to the dog.
Are you sure they are fighting or could they be playing? I know that my cat used to jump forward on a Shep/Rott that I used to have. I thought it was kind of funny watching this. They had done this several times and none of them ever got hurt. Of course, we always monitored this so that nothing bad would happen. To be on the safe side I would keep them separate when your not around.