Newcastle United have agreed a deal worth up to €40million (£34.1m) with Monaco for midfielder Aladji Bamba.The 20-year-old is already on Tyneside, having been given permission by the Ligue 1 club to fly to England to complete a medical.A France Under-20 international, Bamba, who has predominantly played as a defensive midfielder at senior level, has made 25 appearances in all competitions for Monaco since his senior debut last August.Bamba would become Newcastle’s fourth signing of the summer, with the club having already brought in goalkeeper Ewen Jaouen, midfielder Sean Steur and winger Bazoumana Toure.Newcastle missed out on their top midfield target Johan Manzambi, who opted to join Aston Villa instead, and were also beaten to winger Victor Munoz by Liverpool, but Bamba fits the profile of young, hungry players with huge potential the club are looking to sign.Head coach Eddie Howe still wants to sign a new No 1 goalkeeper and at least one full-back, while Newcastle would listen to offers for Joe Willock, who is into the final year of his deal.Newcastle continue to invest in potentialCompleting another signing just before Saturday’s first public friendly against Gateshead will give everyone associated with the club a boost.Bamba, like Toure, Jaouen and Steur, is an exciting addition, a player who has significant room for growth and who Newcastle hope will fulfil his potential at St James’ Park.Aged 20 and with a lack of senior experience, Bamba may need time to really develop and acclimatise to the Premier League, though Sandro Tonali’s exit does mean there is a potential vacancy in deep-lying midfield, even if Lewis Miley is expected to initially step into that berth.Bamba is highly rated in France and seemingly excelled during big-game occasions, so Howe will hope that he can translate that form immediately into the Premier League.Newcastle are keen to push back against the negative narrative which has surrounded the club this summer. Despite losing Tonali and Gordon, and the lingering speculation surrounding Bruno Guimaraes, they are close to completing a fourth signing of the window so far, albeit all of those players are aged 20 or under and so there is no immediate guarantee of success.