Zurich: Fifa warned Liverpool on Monday they cannot play Joel Matip unless Africa Cup of Nations participants Cameroon give the Premier League title-chasers permission.
The key central defender missed Liverpool's 1-1 draw with Manchester United on Sunday amid a disagreement over his international status and he could be unavailable for the next month.
Matip last year announced he no longer wished to be considered for selection by Cameroon and was not named in their Africa Cup of Nations squad.
But the 25-year-old, who last played for Cameroon in September 2015, did figure in a preliminary squad list.
In a statement a Fifa spokesperson told AFP that Liverpool had been directed to study article five of its rules.
It states that "a player who has been called up by his association for one of its representative teams is, unless otherwise agreed, not entitled to play for his club during the period for which he has been released, plus an additional period of five days".
That means Liverpool could be without Matip until they play Tottenham Hotspur on 11 February should Cameroon reach the Nations Cup final in Libreville, Gabon.
In a statement on Sunday Liverpool said it was their view "that the player should be available for club football during the period of the competition and will continue to work for a speedy and unambiguous resolution".
But the Fifa official warned: "Fifa also indicated that any potential violation of the relevant rules would be the subject of an investigation by its disciplinary commission."
Matip has returned to fitness after an ankle problem.
Updated Date: Jan 17, 2017 06:37:21 IST