The Black Cats have agreed a fee - believed to be worth around £700,000 - with Championship side Reading for former Manchester City midfielder George Evans.
But, with the move looking close to completion, it has now hit a stumbling block.
LIVE: Get all the latest transfer news from the Stadium of Light in our blogEvans is believed to be keen to see if there is any concrete interest from Championship sides in his services, with Frank Lampard's Derby County heavily linked over recent days.
On the deal, Sunderland owner Stewart Donald tweeted: “We agree a fee 4 a player & personal terms. We want him Monday to come & sign but he now says he wants to see if he can get a move to Championship!
“Fair enough but we were committed to pay money to sign him. It will happen - I am frustrated too!!”
ANALYSIS: Sunderland take a big step forward - despite transfer impasseMeanwhile, Sunderland have missed out on a move for Cheltenham Town striker Mo Eisa.
The Sudanese hotshot was the subject of a bid from the Black Cats, but the Robins turned the offer down after it failed to meet their valuation of the player.
Eisa has now joined Bristol City, signing a three-year deal at Ashton Gate in a move which sees him team-up with Lee Johnson, the son of his former manager, Gary.
NEWS: Billy Jones targets fresh start after leaving SunderlandOne of Ross' other strike targets - Charlie Wyke - has been dealt a blow having learned that he is set for a spell on the sidelines.
Sunderland have launched a second bid, believed to be worth around £1m, having seen their first offer turned down.
The Bradford City striker is set to spend the next four to six weeks out of action after limping off during the Bantams' pre-season friendly with Sheffield United.
Wyke's injury is not thought to affect Sunderland's interest in him, while Championship sides Bolton and Wigan have also been linked with moves for the striker.