The South Korean winger’s contract with United expires at the end of next season.
He said: “I only have one more year left on my contract and there has been no contact about a new deal yet.
“I want to stay here but we’ll have to wait and see.
“I’m not letting myself become too worried. I just want to concentrate on playing well for United and, hopefully, we’ll talk.
“If I play well and show that I’m an asset to the team then maybe I’ll get a new contract.”