Highy-rated forward Williams has been invited to train with the Wales squad for the friendly with Iceland, but will not be involved in the squad for the game.
The 18-year-old has represented Wales at Under-17 and Under-19 level and he is tipped to make the breakthrough into the senior squad in the future.
Williams, who was born in Milton Keynes, qualifies for Wales through his mother and Chris Coleman is keen to involve him in the senior set-up as he wants to keep tabs on his progress.
Fulham signed Williams from MK Dons in the summer of 2012 and he is highly-regarded within the corridors of power at Craven Cottage.
Williams is the youngest-ever scorer in the FA Cup propers rounds after scoring for MK Dons.