Manchester United have held talks with Bayern Munich over a proposed deal for Jerome Boateng.
Sportsmail reported last week that the 29-year-old had been offered to United after his move to Paris Saint-Germain fell through.
Bayern are prepared to accept around £45million for Boateng, who turns 30 next month, but United want to drive the price lower.
A new centre-half remains the priority and Mourinho is banking on United chief Ed Woodward delivering one.
Boateng — a half-time substitute for Bayern on Sunday night — has emerged as a serious alternative to Harry Maguire who is being priced out of a move by Leicester.
Talks are understood to have taken place between United and their German hosts on Sunday night over Boateng.
United would want to reduce that fee of £45m to nearer £40m.
Asked about Boateng, Mourinho emphasised the need for United chief Ed Woodward to make a new signing.
'The other clubs that compete with us are really strong or they have already fantastic squads like Chelsea, Spurs, City, or they are investing massively like for example Liverpool buying everything and everybody,' said Mourinho. 'If we don't make our team better it will be a difficult season for us.
'My CEO knows what I want for quite a long time, I know he tries to do the best for me and I still have a few days to wait to see what happens.
United have yet to bid for Tottenham's Toby Alderweireld and have grown frustrated in their pursuit of Barcelona's Yerry Mina.
Everton have since agreed a £28.4m fee for the Colombian - though the deal is still to go through.
Elsa98
36
I would rather bayern keep boateng, but i think man utd really needs him to boost the defensive line! Bayern will survive without boateng, yes they will.. They will just replace him with some bundesliga talent! Please get this deal done, i feel pity for mourinho.. Maguire is staying, toby and mina are uncertain..
Patrickkim12
32
Defence defence defender, bus, pack the bus. lose the game 😅😅😅😅😅