Roberto Martinez insists there is no "war" with Manchester United over the fitness of their Belgian players, despite Marouane Fellaini's quick return to action.

Fellaini was not available for selection for Belgium's upcoming matches with Iceland and Switzerland due to a lack of fitness following a groin problem.

However, United boss Jose Mourinho was forced to start Fellaini for the weekend Manchester derby due to a thigh injury suffered by Paul Pogba.

Despite not being fit for international duty, Fellaini played the full 90 minutes in United's 3-1 defeat, which could have left Martinez wondering why he was not allowed to call on the 30 year-old.

The former Everton boss has no problems with United's decision and rejected claims there was tension between the two parties.

"What happened with Marouane Fellaini is something that happens constantly in dressing rooms," he told a media conference.

"Due to the circumstances, he had to play, and it's incredible to see him playing 90 minutes at an incredible level, so for us it is fantastic news. 

"We made a decision last Friday about the squad with information we had on all the players and it is a good opportunity to carry on with the plans that we have. 

"But knowing that Marouane played 90 minutes at the weekend is good to know, it means that he is getting very close to being fully fit and if he is needed he will always be available to the national team. 

"The two medical departments had very good conversations and the best decision is the one we took. There's been nothing strange about the situation of Marouane.

"It's good to see he got through the 90 minutes. We are delighted he is getting [back] to his best level, the same way that we were disappointed he couldn't participate with us in the previous camp because of the niggles.

"That was a disappointment we shared with his club. We are working all together, this is not a war [with Manchester United], this is not a situation where we are trying to get revenge over anyone."

Another United star, Romelu Lukaku, will be rested for the friendly with Iceland as he continues his recovery from a hamstring strain.

But Martinez could use the striker against Switzerland as Belgium look to reach the Nations League Finals.

"Romelu will train today with the group," added Martinez. "He's had a very positive reaction so we'll take it day by day, see how he feels and we'll take it [him playing] into consideration."