Celtic have rejected an offer for Olivier Ntcham from Porto worth more than £13 million ($17m), Goal understands.
The Scottish side are determined to hold on to the 22-year-old midfielder, who joined from Manchester City for around £4.5m last year.
However, the Portuguese side are expected to return for the France Under 21 international after being knocked back in their initial attempts to sign him.
Ntcham is said to be interested in making the switch to the Primeira Liga and his agent will hold a meeting with Celtic on Friday.
Although their offer of £13m plus bonuses fell flat, Porto will return with another bid, but they are only willing to wait until next week to complete the deal.