Manchester United have reportedly stepped up their interest in Jerome Boateng by making an official enquiry for the Bayern Munich centre-back.

The Red Devils are expected to strengthen their backline before the new season gets up and running in a little under three weeks' time as Jose Mourinho remains unconvinced by Chris Smalling and Phil Jones.

Boateng is one of numerous players to have been linked with a move to Old Trafford, with Bayern making no secret that they will be happy to cash in if the right offer is made.

German outlet Kicker suggests that United have now made an 'initial exploration' over a deal for the 30-year-old, and they have been informed that a fee in the region of £53m will suffice.

However, the same report indicates that Mourinho's men could face serious competition from French champions Paris Saint-Germain.