United have so far spent upwards of £150m on Romelu Lukuku, Nemanja Matic and Victor Lindelof this summer.
The Red Devils are now fully expected to make a serious challenge for the Premier League title and compete in the Champions League as well.
Mourinho has hailed his club for getting ’75 per cent’ of their business done and dusted before the new season bursts back into life.
But the United boss admits he’d like one more new arrival at Old Trafford before the transfer window slams shut.
He said: "I’m happy with the effort the club did, I'm happy that the club managed to do 75 per cent of the work before the Premier League starts.
"And if, until 31 August, the remaining 25 per cent don’t arrive, I will not moan.
"I will just go with everything I have to try to win every match we play."
While Mourinho is delighted with United’s trio of summer signings, he admits he still wants a new winger.
The Special One added: "We got a central defender that can play in many other positions, which is important. Victor can play right-back and can play centre midfield.
"We got a centre midfielder, we got a striker.
"Obviously [we wanted] a player for another position playing from the sides, but we have players and if you cannot strengthen the team in these areas, we have people that we trust and we go for it."
United take on West Ham on Sunday at Old Trafford as they kick off their new Premier League campaign.
