Barton fully expects to join the newcomers when the players return for pre-season training next month, and he revealed his decision to reject a contract offer in January had nothing to do with money.
He said: "I am 28 years of age and I think it's an important contract for me. My partner has just found out she is pregnant with our first child, so I need a little bit of stability, I need to be in this area for four years.
"I was after a little bit of stability. The money side of the situation was never an issue for me. I was keen to stay in Newcastle, keen to stay in the area.
"We never reached a compromise on that, unfortunately, and it became quite frustrating in the end.
"I was quite surprised, quite taken aback by it, but I was quite realistic.
"Look, this is football. I believe in the ability I have and I believe in the man that I am.
"If that's the case, if Newcastle United don't think I'm going to play past the age of 29, then more fool them.
"If I have to go and ply my trade elsewhere, then I'm more than confident of being able to do that for the next six, seven years.
"Nothing would mean more to me than to do it at Newcastle United, but if that's not the case, then that's not the case."