Home Loan Question?

I am purchasing a home currently, but I have not closed, nor have I signed any doents finalizing anything... I have placed a deposit only for $6,000. The house has now been appraised under what the company is selling it to me for(kbhomes)... Because of this, the loan company (Countrywide) is wanting to change my loan from 100% to now wanting me to put 3% down. Before this everything was fine, I have already been approved for the total amount of the home loan (100% financing), we're just waiting to close and the house to be finished. But now CW wants to change up the loan... is there anything I can do? I don't think i should have to put anymore money down.