Of course, if you are working with an agent, they will inform you of the best options for you.
Hopefully you're working with a Realtor. Have your Realtor ask the listing agent for an extension - explaining the reason(s). All parties will have to agree and sign the extension. If the seller doesn't want to extend the contract, they don't have to but in today's market, they may be willing to (depending on the reason for the extension).