United manager Sir Alex Ferguson is believed to be eyeing Diarra as a replacement for the injured Owen Hargreaves and veteran Paul Scholes.
But Diarra has played the last four games, and Mourinho said: 'He has played well recently.
The Real deal? Diarra in action against Getafe on Monday
'He was even in the starting XI while usual midfielders were available.
'That proves I want him to go on here.'
Diarra is on contract with the Spanish giants until 2013.
He previously had spells with Arsenal, Chelsea and Portsmouth.
Real Deal: Fergie targets Madrid star Diarra as long-term midfield solutionManchester United the big winners on a night when they didn't even playMANCHESTER UNITED FC