If the lender comes back with a counteroffer, if the seller will go along with it, give a counteroffer to their counteroffer.
Some Sellers at the advise of their listing agent may not try a counteroffer back and may simply put the property back on the market at the approved price and list it as being "approved at the asking price".
I believe if Fannie Mae is the owner of the mortgage (you can look it up online by address) then the "servicer" for Fannie Mae is "required" to give a counteroffer. Just closed a fannie mae short sale and that's what they did. The buyer countered it and my seller was okay with trying a counter (it was still in the ballpark) and Bank of America (servicer, not the owner of the mortgage) accepted the buyer's counter. It was a simple short sale as there was only 1 mortgage (with Fannie Mae as the investor/owner) and a true hardship case.
Just as an fyi... there is no relationship between what a seller "owes" on his mortgage(s) and what sale price will be required. The "current market value" versus the offer amount is what the Negotiator for the lender will look at. What is owed is meaningless because the "market" will dictate what they can sell it for if the lender decides to foreclose instead of allowing a short sale.
And remember, keep shopping for a home while you are waiting for an approval that may NEVER happen.
All the best,