The takeover was revealed on June 10 but the Owls kick off at Brighton today in the Championship still unclear over who will be their future owners.
Azerbaijan businessman Mammadov has “issues” in his homeland which are delaying him completing the deal and has apologised for dragging out the takeover.
Mandaric insists he will support coach Stuart Gray in the interim and hopes to use the money from this week’s £1.5m sale of Michail Antonio to Nottingham Forest to bring in “two or three” players before the transfer window closes at the end of August.
On the takeover, Mandaric said: “Unfortunately, despite much hard work from both parties Mr Mammadov has not yet been able to perform his obligations under the terms of the agreement.
“We continue to have dialogue with both Mr Mammadov and his advisors and we are hopeful that the issues he is dealing with in Azerbaijan, which are delaying his ability to complete the deal will be resolved and that he will fulfil his obligations within a reasonable timescale.
“During my recent meeting with Mr Mammadov in London, he gave me his personal assurance that he intends to complete the deal as quickly as possible and has apologised for the delay which is clearly causing concern to the supporters of our club.
“I still believe that Mr Mammadov will be a wonderful owner of this football club and his vision for the future compels me to resist any temptation at the moment to terminate the process and open new discussions with other potential interested parties who have contacted me during the process.
“I shook Mr Mammadov’s hand and my word is not something I renege on.
“Clearly, there may come a time when I am unable to allow the process to continue, the stability of the club is of paramount importance to me and I do understand how the uncertainty of ownership can become a negative force if allowed to drag on.
“I would like to assure supporters that whilst this process is ongoing I will continue to give my full support to Stuart and his plans for the forthcoming season.
“We have a fine squad and I hope with the addition of two or three more players before the window closes we will be in a position to mount a strong challenge this season.”