Swansea have rejected a bid from Everton worth up to £10m for captain Ashley Williams.
Williams, who turns 32 later this month, is contracted to Swansea until 2018.
A Swansea spokesman said: "Ashley Williams is an important part of our squad and club and we are not looking to sell him, and therefore we have turned down the offer currently on the table."
Everton manager Ronald Koeman has targeted the Swansea captain to bolster his options in central defence.
The Toffees are engaged in negotiations with Manchester City over the sale of John Stones and are understood to be asking for £50m for the England international.
If Stones does depart Goodison Park, Williams would offer an experienced alternative but chairman Huw Jenkins is reluctant to lose a player who has emerged as a pillar for both club and country in recent seasons.
Williams has made close to 350 appearances for Swansea since joining from Stockport in 2008 and led Wales to the Euro 2016 semi-finals earlier this summer.