1)do you have an escape clause allowing you to back out within a certain period of time?
2)let the other party know as soon as possible that something has come up that you cannot buy the property, apologizing for the inconvenience caused and seeking for other party's understanding;
3)I could not believe you have not paid the earnest money when your signature was inked. That may make your life easier.
Good luck
Let me know if the other party rejects your request.
