West Brom have refused Cardiff permission to play midfielder Jason Koumas in their FA Cup clash with Arsenal at Highbury on Saturday.
Koumas is on loan at Cardiff and Albion boss Bryan Robson does not want to jeopardise his availability for the competition should a rival club meet their valuation of the player during the January window and sign him on a permanent basis.
Cardiff have first option on signing Koumas permanently - providing they pay the undisclosed fee Albion agreed with them last summer.
But the Welsh club have so far failed to complete this agreement.
West Brom chairman Jeremy Peace said: 'We're more than happy to sell Jason to Cardiff in line with the terms of the deal we agreed with them in the summer.
'Jason would then be free to play for them in the FA Cup. Until such an agreement has been reached with Cardiff, we will not grant him permission to play in the competition.
'Should another club be prepared to pay the same price for Jason, we will then be happy to discuss a deal with them.
'This would allow Jason to play for them in the FA Cup should they remain in the competition.'