dominance/territorial behavior

I am in desperate need of some guidance. We have a 3 y.o. pit bull rescue we got when he was a year old. He is absolutely full of self will. He is very territorial around his kennel and the bedroom where the kennel is. He will show aggressive behavior when being put into the kennel or if he thinks his space is being violated.Example: If he is standing by the bed and I approach he will growl and then go into the kennel.We have had near misses and he has actually bitten me on a few occasions when he has felt his space is being threatened.Not bad bites,thank God. But I need to correct him and I am at a loss as to how to do this.Any suggestions?

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