"Rio has assured me that if the position remains as it is he will give his full commitment as a player and captain to Leeds United."
However, Ridsdale has said that if United matched their valuation for the player they paid £18m for, then he could be allowed to leave.
He said: "We received an offer some weeks ago, but that was rejected out of hand as we felt it to be derisory. But we are a public company, I am merely an employee and I have a duty to shareholders to maximise the value of our assets.
"If we receive any reasonable offers for any of our players, including Rio, we will consider it and debate it, but that is not the position at the moment.''
To secure the England centreback's services, United seem certain to have to break their own British transfer record of £28.1m, which they paid Lazio for Juan Sebastian Veron last summer.
United manager Sir Alex Ferguson is keen to get the deal done as quickly as possible and he has said that he may be forced to go after one of his other defensive targets if things continue to drag on.
