Absolutely. Yours is the classic case for which the remedy of "specific performance" is granted. Hire a real estate attorney to write seller a letter (or write it yourself). Say that if seller doesn't close (before you lose your financing or your rate goes up), you will sue him. The court will force him to close the sale, then make him pay your court costs. If the sale contract said anything about it, you might get attorney fees also. Finally, if you have to refinance & are damaged thereby, you can make seller pay you the extra money you have to pay. Upon reading this letter, seller will likely close the sale. If he doesn't, sue him immediately.
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This is not legal advice and you are not my client. Double check everything with your own attorney and your state's laws.