1. I wonder how one can agree to sell the land without even written agreement.
2. Since there is no written agreement you can take plea of expiry of time without much difficult as though the verbal agreement is also valid , it often raises this type pf complications if disputes arises in future.
3. Send the buyer a legal notice repeating the terms of the verbal agreement and ask him to make the balance payment within 7 days in default of which you may mention to cancel the agreement and take possession.
4. DO not give him any extra time and keep continue the pressure on him.
5. To exert more pressure inform the local police and bring this to the notice of the buyer.