However, Owls chairman Milan Mandaric remains hopeful the deal will be completed after a meeting with the Azerbaijani businessman in London last Friday.
The statement on the club's official website read: "Further to the press release on Tuesday 10 June, Sheffield Wednesday would like to update supporters on the current position in respect of the takeover of the club by Hafiz Mammadov.
"Unfortunately the planned completion date has been delayed slightly due to some important matters relating to the other business interest of Mr Mammadov which have required his full attention in Azerbaijan.
"This has delayed him from travelling to the UK as he had originally planned and hindered his ability to conclude the takeover.
"During this time, however, the due diligence process has been completed and we will hopefully soon be in a position to complete the regulatory requirements set by the Football League.
"Mr Mammadov's advisors have been in constant dialogue with the directors of the club and an excellent working relationship has been built between both sides.
"We are pleased to confirm that Mr Mandaric and Mr Mammadov met in London on Friday evening to discuss the takeover process and both parties confirmed their commitment to complete the sale as soon as practical."
Mandaric added: "I fully appreciate the frustration of our supporters, we all want to see a quick completion so we are in the best shape possible for the start of the new season.
"Despite the delay, I am still committed to fully supporting (manager) Stuart (Gray) in his preparations and this has been demonstrated by the permanent signings of Keiren Westwood and Sam Hutchinson along with the contract extensions agreed with Chris Kirkland, Glenn Loovens and Jose Semedo.
"I have been kept fully informed by Mr Mammadov's advisors during the process and Friday's meeting was very constructive. I continue to believe that he will be a wonderful custodian for this great club and I am very excited at his plans for the future."