Smalling wants to return to Roma after spending last season on loan at the Stadio Olimpico and has been training away from the rest of the Manchester United squad.
But negotiations between Manchester United and Roma have dragged on several months and have become exhausting as the two clubs continue to haggle over a fee.
Manchester United have not lowered their asking price from €20m and Roma’s last offer for the defender was little over €12m, including add-ons.
Roma are plotting a fresh and final assault to land Smalling and according to Italian daily Il Tempo, the Serie A giants dispatched a market intermediary to England from Italy on Tuesday.
The Giallorossi have not given up hope of signing Smalling and are hopeful that the intermediary will find a way to unlock the negotiations.
Roma have other alternatives to Smalling but they have all been kept on standby as the Serie A giants make one last-ditch attempt to sign the 30-year-old defender.
Manchester United do not want to drop their asking price for a player who proved himself as one of the best centre-backs in Italy last season.