Sunderland have confirmed that the League One club has been put up for sale by owner Stewart Donald.
The Black Cats have stated that it was pressure from upset fan groups which led to the board making their decision.
A joint fans' statement calling for the club to be sold immediately has led to confirmation of the story reported last week by BBC Radio Newcastle.
"The board feels that it has no option but to sell the club. That process has now commenced," read a statement.
"Owing to confidentiality agreements, there will be no further updates until a preferred bidder is identified."
The club also made reference to Donald's "sincere commitment on his arrival at Sunderland that 'I won't outstay my welcome'."
Donald bought the club from American Ellis Short in the summer of 2018 following relegation from the Championship. But they then failed to win promotion back at the first attempt, losing to Charlton Athletic in the Wembley play-off final through an injury-time goal.
Sunderland are ninth in the table, just a point off the top six following a successful festive period in which they extended their unbeaten run to five games.
Donald owned National League club Eastleigh before taking on the Wearsiders.