Building Work STOP No sign of possession on time

I have booked a flat in 1 of the prime location nearby Powai Gandhi Nagar, a SRA Project & as per Agreement it should be delivered by Dec15. Since last more than 1 year WORK is Stand still even though mine is Salable tower & SRA allotment was done to Slum tenants. As per Our Agreement the possession date is of Dec 15. is there any way legally ask builder to Start the work or pressurize builder for timely delivery. He told as fund issue for A & B wing & bankers are not willing to invest unless he has C wing CRZ clearance which again has DP dependency. All the required approvals for A & B is there & he can even get part OC for part possession but, all things are stand still due to FUNDS i guess which is not at all ,my concern. Saleable tower is of 3 Wings & A & B 22 story structure is ready & C Wing Environment clearance is pending & All internal & external work pending for both A & B Wing. Builder says as he will do all remaining work of A & B in time which is very doughtfull & not possible as only 4 mths are left. What are the options & ways after Dec 15 if possession is not given?