Issue in notice period

I am currently working in an IT firm by third party payroll and in the offer letter provided by the third party I must serve a notice period of 60 days and full details are below: 11. Separation: In the event you wish to leave the services of the Company, you will be required to give a clear written notice of 60 days to the Company. You will be relieved from the services of the Company subject to your: a. Handing over the project and knowledge transfer to the client’s assigned representative/s in respect of the assignments handled by you. b. Obtaining a “No Objection Letter” from the client as a confirmation of your having complied with (a) above. You are bound to make good the loss suffered by the Company and/or Client and any other charges/liabilities the Company/client incurs, if you fail to give such written notice and complete the handover within the prescribed time as mentioned hereinabove. Should exigencies of business so dictate, the Company may require you to serve the entire or part of the notice period as mentioned above. However, I got a good opportunity for another IT firm as direct employment but, they want me to join in 30 days. I had sent my resignation letter to my hiring company however, they are not willing to accept it. What should I do now