Newport County are bidding to have on-loan goalkeeper Karl Darlow available for their FA Trophy Final at Wembley Stadium against York City on 12 May.
The Exiles have been unable to win their case via the Football Association and its Welsh counterpart and have approached Fifa.
Newport claim Darlow, 21, signed from Nottingham Forest before the 9 March international clearance deadline.
But the Welsh club say a paperwork delay was not their fault.
Englishman Darlow said: "The club think there's a very good chance now, a very good chance.
"They've got a lawyer involved and it's moving along quite well, as far as I know."