Manchester United boss Jose Mourinho is concerned over their preparations for next week's derby with Manchester City.

A number of Mourinho's first-team squad are away with their national teams in the build-up to the showdown with Pep Guardiola's side at Old Trafford on September 10.

He told MUTV: “We keep eight outfield players and Sam Johnstone as the goalkeeper.

“We are going to lose the others and we don't know the way they train, the way they recover, the life they are going to have with their national teams.

“Some are coming back on the Monday before the Manchester City match but some are coming back on Friday. The day before Man City, we will still have Sergio Romero, Marcos Rojo and Antonio Valencia arriving.

“It will be a complicated process but we know it is like this when we have these players. And I would love all of the players to go because it would mean that everybody is being selected for their national teams."