Manchester United could become embroiled in a row with Belgium after Marc Wilmots, the national coach, insisted that Marouane Fellaini will train on Tuesday with a splint on his injured wrist before a prospective appearance in Friday's World Cup qualifier against Croatia.

Fellaini, who has suffered strained ligaments in the joint and requires surgery, is expected to be out for several weeks so United's preference would be for the procedure to happen as soon as possible so that the midfielder can start his recovery.

However Wilmots' stance that Fellaini should play for Belgium first means it will be longer before he is available again to David Moyes, the manager. Under Fifa rules Fellaini is currently under the jurisdiction of the Belgian Football Association, rather than United, due to the international break.

"Marouane Fellaini should be able to play for Belgium against Croatia in Zagreb on Friday," said Wilmots. "Marouane has suffered wrist ligament injury and will have to undergo surgery. He will join the squad and train on Tuesday with a splint. As far as I am concerned, in principle he is able to play Friday. This does not mean that he will automatically play. I have not heard from Manchester United asking that the operation should be as quickly as possible."

With Fellaini having been United's sole summer signing, the loss of a player who cost £27.5m for any prolonged period represents a sizeable blow to Moyes, especially given the paucity of alternatives he has in central midfield.

Beyond Michael Carrick, Tom Cleverley and the veteran Ryan Giggs, the Scot has no other regular first-team players for the positions with the Brazilian Anderson a reserve at best.

This means that United's summer transfer policy will again be called into question after the window ended with only one of the two central midfield additions Moyes had decided were required having arrived in the form of Fellaini.

Fellaini suffered the injury in United's 1-1 Champions League draw with Shakhtar Donestk last Wednesday. This caused Moyes to leave him out of the 2-1 win at Sunderland at the weekend before Fellaini had a scan in Manchester on Monday.

With the champions expecting this to indicate that surgery would be required, Moyes wanted the 25-year-old to avoid any risk of further aggravating the injury by playing.

Following the win over Sunderland Moyes said: "He's got a wrist injury. He's going to see a specialist. It doesn't sound too good but we'll wait and find out on Monday."