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.

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."