The Italian took over the Championship club in February but was disqualified by the Football League a month later after a court in his homeland found him guilty of the non-payment of import duties on a boat.
Former Cagliari owner Cellino successfully appealed the decision in April but, following full disclosure of documents from the Italian court, the Football League ruled that he was in fact subject to a disqualifying condition and demanded that he resign within 28 days.
Cellino has since lodged an appeal to the League's Professional Conduct Committee, meaning he will not be required to step down until two days after the hearing, which takes place on January 15.
It was initially announced that Cellino would be disqualified from 'holding office or acting as a Relevant Person' in respect to Leeds until March 18 should the judgement stand.
However, it has now been agreed that the sanction will be "extended by an amount equivalent to the length of time between December 29 and the deferred deadline" if Cellino's appeal fails.
A Football League statement read: "The Football League and the legal representatives of Leeds United president, Massimo Cellino, have agreed the process and date of Mr Cellino's appeal against the decision by the Football League Board that he is subject to a disqualifying condition under its Owners' and Directors' Test.
"The matter will be heard by a Professional Conduct Committee (PCC) chaired by Tim Kerr QC on January 15.
"The original decision required Mr. Cellino to resign as a director of Leeds United and cease acting as a 'relevant person' in line with Football League regulations by December 29.
"The League has agreed to defer that deadline until two days after the handing down of the final decision of the PCC. As a consequence, the parties have agreed that if Mr Cellino is unsuccessful in his appeal, any disqualification period will be extended by an amount equivalent to the length of time between December 29 and the deferred deadline.
"The parties have agreed to make no further comment prior to the hearing of the PCC on January 15."
