Swansea City have been denied international clearance from Fifa to finalise the signings of Darnel Situ and Rafik Halliche.
The Premier League new boys had agreed deals to bring in Halliche on loan from Fulham and Situ from Lens in a £250,000 transfer before the summer window shut.
However, manager Brendan Rodgers has been unable to field the duo whilst awaiting the green light from the world game's governing body and, due to minor delays in processing the transfers, the South Wales club have now been informed they will not be granted international clearance for either defender.
Fifa's decision comes despite Swansea having the full backing of the Premier League, the Football Association of Wales, the FA, the French Football Federation and the Professional Footballers' Association.
Swansea will await official written confirmation from Fifa before considering whether to appeal, having previously been given clearance for the deal which has brought Fede Bessone back to the club.
A Swansea statement read: "Swansea City is disappointed with Fifa's decision and are currently pursuing other options to strengthen the squad.
"The club will not be making any other comment at this stage until full written clarification is received from Fifa."
Failure to land the two defenders comes at a particularly inopportune time given an injury which will keep Steven Caulker sidelined for two months, though club captain Garry Monk is close to a return.
It is now understood that Fulham have applied to the Premier League for special dispensation to add Halliche to their squad, although their request will depend on whether Swansea successfully appeal Fifa's decision.