STEWART DONALD is hoping to complete a sale of Sunderland before the start of the new season in mid-September after agreeing a period of exclusivity with one of the groups jostling to try to buy the club.

However, with a final sale price still be agreed, and the terms of any deal another potential sticking point, there are still a number of substantial obstacles to be overcome before Donald’s time in charge of the Black Cats finally comes to an end.

Having reiterated his desire to sell up when he publicly confirmed his £37.6m asking price a week-and-a-half ago, Donald has spent the last few days in discussions with a number of interested parties.

He is understood to have shelved discussions with Mark Campbell for the time being, with concerns over the credibility of the US-based businessman’s bid having not been adequately allayed. Campbell had hoped to have started a formal process of due diligence by now, however his attempts to engineer a deal have not reached that stage.

Similarly, while energy drinks entrepreneur William Storey has made some very vocal comments about his interest in Sunderland this week, his initial approaches have not resulted in an agreement.

Storey, who is the CEO of Rich Energy, claims to have assembled a team of “blue-chip backers” to try to buy the club, but as ever with takeover situations, his willingness to use his interest to bolster his public profile has set alarm bells ringing.

With the intentions of former Birmingham City vice-chairman Sammy Yu still shrouded in mystery, the two competing groups who appear to be in the best position to push through a deal are the group being headed by former Sunderland defender Michael Gray and a rival North-East based consortium that is known to have held a number of discussions with Donald in the last fortnight.

While Donald has not made any public comments on the state of his talks, it is believed that one of those groups has been granted an exclusivity period in which they and they alone can attempt to force through a deal.

Gray, who has spent the last few years working as a co-commentator on talkSPORT, confirmed last week that he had held discussions with director Neil Fox, a close associate of Donald, and was working to try to broker an agreement.

The former full-back will not be investing any of his own money into the consortium he is involved with, operating instead as a go-between linking various members of the group, but as well as acknowledging Donald’s £37.6m asking price, he also accepts there will be a need to invest almost as much money again in order to make Sunderland a viable proposition in first the League One promotion race and then the Championship.

“Still processing figures to see if we can come up with a solution,” tweeted Gray last Thursday. “As you are all aware, it is very complicated. This will not sort itself out overnight. But I’m doing everything I can to help, succeed or fail I’m trying.”

Gray’s group faces competition from a rival consortium that is known to feature at least one prominent figure with deep-rooted links to Wearside. There has been considerable speculation that John Hays, the founder and chief executive of Hays Travel, could be involved in some capacity, but that remains unconfirmed at this stage.

While Donald is focusing his energy on trying to tie up a sale, Sunderland boss Phil Parkinson is working to try to assemble a new squad for next season.

Having confirmed the retention of Tom Flanagan on a new two-year deal at the weekend, Parkinson is hoping to agree a deal with another central defender, Bailey Wright, this week. Wright, who spent the second half of last season on loan at the Stadium of Light, is a free agent following his release from Bristol City.

Flanagan’s previous Sunderland deal expired in June, but having made more than 60 senior appearances in the last two seasons, the 28-year-old is delighted to have extended his stay on Wearside.

“It’s been an uncertain time in every sense, so it’s good to have it signed and sealed,” said Flanagan. “I’ll be raring to go once we return to training.

“I get on really well with the manager, and I like his management style, so I’m really looking forward to the next two years. There is definitely unfinished business for me at the club, so I can’t wait to be back.”