The Blues have been tracking the influential midfielder for a number of months and are desperate to make him their twelfth summer signing but have issues matching the Swans’ £50 million pounds asking fee.
Speaking after Everton’s 1-0 win over MFK Ruzomberok in the Europa League, Koeman told ITV: "It's up to the board. Everyone knows our interest in the player but I don't decide it in financial terms. It's up to the board.”
Everton have already reportedly bid twice for Sigurdsson - one in the region of £40 million and the other totalling £45 million - but have been rumoured to return with a penultimate bid just short of the full asking price in a bid to test the Swans resolve.
Earlier in the week, Koeman said that any further transfer business was not subject to the sale of Ross Barkley and he still had funds to work with but his squad needs a striker and cover at centre-back.
Playing the transfer game
If Koeman’s interest is as high as believed, Everton will do all they can to get their man from Swansea like they did when the 54-year-old nigh on demanded they sped the process to sign Morgan Schneiderlin from Manchester United last January.
At that point, the Dutch boss had seemingly grown tired of his team’s inability to get a deal over the line but after laying down an ultimatum to bring players in, the Blues acted.
This summer, Everton's director of football Steve Walsh and the board have moved quickly to secure a number of key targets - even getting permission from both the English and Spanish FA’s to sign players on international duty at the U23 European Championships.
Koeman’s desire for swift business has seen the Toffees drastically improve the speed in which they get deals done but the Sigurdsson saga may just see the 54-year-old lay down the law yet again.
Viera, 27, is being touted as Swansea’s replacement for Sigurdsson but the Spaniard has been linked with Everton in the Spanish press for a number of weeks.
The Blues have also again been linked with another move for Viera’s teammate Mauricio Lemos as they go in search of defensive cover for the injured Ramiro Funes Mori.