I am having an issue with my current employer, regarding my

Sir, Currently I am having an issue with my current employer, regarding my releasing date. I have resigned from my current organization, I have to join other. as per the offer latter it is mentioned as below "In the event you want to terminate your employment with company, while in a project at customer site in India or abroad you will require to give a minimum of 60 days notice, to enable smooth transition and transfer of technology, the actual date of release will be mutually decided with consent of the concerned client and your superior and the said date of release shall not be unreasonably withheld provided you are able to handover charge satisfactorily with in 60 days of period. this minimum notice can not be adjusted against with Privilege leave" But my organization is asking for 90 days, it is going to affect my feature assignments. I need help regarding this.