Options if seller has 'seller remorse' on the day of close?

[Edward Liu]

Today is close day for one of my purchases in NC.  However, despite I completed everything needed from the buyer end (all the money is with closing agent, etc.), seller is refusing to sign final documents and close the deal.  

Seems seller realized that agreed purchase price is about 20-25% below market.  Listing agent said today that they intend to fix up couple things and put it back onto the market.  

I have never encountered 'seller remorse' on the day of close.  Obviously I have put in money and time for inspection, appraisal, etc.  Best case is I want to finish the deal as it is a good buy, worst case is I want to recuperate cost and time spent (mine, my agent, title company, my 1031 exchange, etc.).  

Any options for next steps? Can I force seller to sell to meet the contract obligations?