Ajax coach Frank de Boer says Manchester United will have to pay a "huge price" if they want to sign goalkeeper Jasper Cillessen.
The 26-year-old is a confirmed target for boss Louis van Gaal who kept regular goalkeeper David De Gea out of his squad for Saturday's match against Tottenham Hotspur.
But the Red Devils will have to make a very important bid if they are to secure the services of the goalkeeper because Ajax are determined to keep him at the club, as confirmed by de Boer.
"Man United will have to pay huge price for Cillessen," De Boer is quoted as saying in the Mirror.
"Let it be clear that we are going to take a really strong attitude and we will fight against him leaving at this stage.
"Why? Because we have seen all our three alternatives go out of sight and it gets harder and harder to find a decent replacement.
"To make it clear, Jasper is getting more expensive by the week, although there are certain figures that we can't turn down."