Your problem sounds interesting. It sounds like he is biting just so he can play tug-of-war. Something you don't want to do.

A modification. Turn your puppy on it's back. Don't say anything. Place your hand between it's front legs and hold the dog steady. You are not playing. That is a very vunerable position for the dog and won't like it much if it isdominant. A dominant dog will fight tooth and nail, growl and try to bite. A playful dog will think it is still a game. If it doesn't growl and fight but just want to be released then it is non-dominant. It is just distracted and wants to do something else. A dominant dog will need a harder hand in training in the future, firmer voice and more patience.

I would suggest you get the DVD I mentioned in your other post. It does a good job on conditioning your puppy using a light hand. It talks about crate training, using the table, chain gang, etc. Most of the stuff books will leave out.

Remember, never give in until the dog/puppy complies with whatever your teaching.