In godfather 2 why does Hyman Roth want Michael dead?

This movie was confusing but upon second viewing i pretty much understand everything but this, like i remember Mike said to Fredo in Cuba about how "he treats me like his succesor and he thinks he'll live and he wants me out" and Fredo revealed later on to Mike that Mike was being tough on negotiations and they needed Fredo's help ? So is it out of greed or he wanted to close the deal in Havana faster?