When Crate Training A Puppy, What Do You Do When He Won’t Accept The Crate?

I am housebreaking a 12 week old puppy using the crate training method. He hates the crate and immediately starts whining, worrying, clawing at the door, etc. He is normally a very calm and contented puppy. What can I do to make this more acceptable to him, both for housebreaking and for other times he needs to be crated? We have not put him in the crate for more than a few minutes at this point, because he is so incensed about it! If it has any bearing on your answer, he’s a cockapoo.