Ltcg tax-exemptions

Dear Sir, We sold our residential flat on 30-11-2012 and got Long Term Capital Gain and the money was invested in purchasing a flat of an under construction project(under Group Hosing of about 2000 flats in Noida in U.P. We have paid 95% of the cost. But the project is delayed and not in a position to give possession within 3yrs from the date of sale, as the Builder are claiming that this delay is due to NGT and other Government issues. Is there any grace period for giving LTCG Tax beyond 3 yrs, for this type of delay, due to the Government Policy? It is known, exemption u/s 54, allottee of DDA and cooperative societies gets the extension beyond 3yrs. Please confirm our case. Aruna Sen