Ranson insists he will not let star Westwood leave for free next summer with a host of Barclays Premier League clubs understood to be chasing his signature.
The Republic of Ireland stopper, 25, was the subject of a failed 11th-hour bid from Tottenham for his services back in January.
"All it is at the moment is speculation, we are desperately trying to get him to sign a new contract as he's got 12 months left," said the Sky Blues chief.
"Until he or his agent turn around to us and say he's definitely not signing a new contract then we are very optimistic.
"But there is interest in him and rightly so, he's an international goalkeeper now and he's the best goalkeeper outside the Premier League - and he's only getting better.
"So it's no surprise all the big clubs want him. We're not soliciting any firm bids but we are expecting it now the window's opened."