Xhaka has agreed terms with Hertha Berlin for a January move.
But Arteta insisted last night: "Yes, he did [give me that reassurance].
"I think he is going to stay. He was very good [against United], and I really like him. With the way we want to play, if we get him on board I think he can be a tremendous player for the football club.
"I like everything about him. His commitment, I like the way he is, the way he lifts his profession, how focused he is. Every time I am talking, he is listening and is willing to learn.
"He is a great football player. The way we want to play, there are not many with his quality on the ball, his range of pass, so I am delighted to have him."