Sheffield United are looking for a new Manager after Gary Speed resigned from his role at Bramall Lane to become the new Wales boss
Speed, Wales most capped outfield player, took over the Blades hot seat in August after the departure of Kevin Blackwell.
United are currently 20th in the npower Championship and lost for the second match running, to Barnsley, at the weekend, having won their two games prior to that to stay just above the relegation places.
The 41-year-old replaces John Toshack as Wales Manager who resigned in September after a 1-0 defeat at Montenegro in a Euro 2012 qualifier.
Sheffield United's Chief Executive Trevor Birch told www.sufc.co.uk: "This has been a difficult decision for Gary. After only four months in the job he felt he had very much unfinished business but ultimately was ruled by his heart and decided to take an opportunity which may never have come his way again.
"We are obviously disappointed and this would not have been entertained had it been another club side but having received the approach we felt obliged to give Gary the option of discussing the position with the Welsh FA.
"We didn't want to lose him but we have to respect Gary's decision given the uniqueness of the opportunity. This is a prestigious appointment and we wish him every success and thank him for his contribution to the club over the last three years."
First team coach John Carver has been appointed as Caretaker Manager and he will assisted by Sam Ellis and club captain Chris Morgan.
For all the latest news on Sheffield United please click here