Request To Extending Joining Date

Dear friends,
Please help me in drafting letter to extend my joining date in Kerala PSC as I am working in Middle east. I need an extension of leave for 6 months. The reason is the the present employer in middle east need 3 or more months prior notice to release me from job. I hope some one can help me to draft a nice letter.
thanks

First thing is that you are asking for a letter to inform Kerala PSC that you are allowed to join them after 3 months or later bcz you are employed outside and you need to serve notice period of 3 months to your present employer. But where comes leave or extension of leave in this case bcz you are not an employee with them yet and asking for extension in joining date.
Well you just need to draft a simple letter that you are happy that you gonna join them but as per your current employment rules, you are not allow to leave before serving 3 months of notice period that you already have done (if it is done), therefore you are requesting them to allow you to join them after completion of this notice period/ 3 months (Or minimum less time you required to join them).
Also you can mentioned the reference of your current employer/Boss and need to have tele-communication with your future employer.