The German international's deal ends at the end of next season and his club are desperate not to lose another of their prized assets. Borussia Dortmund are determined to keep midfielder Ilkay Gundogan out of Manchester United's clutches. Gundogan is out of contract at the end of next season and Dortmund are keen to tie him down with a new deal. The Germany international has been out since August with a back problem and Dortmund do not want to lose another one of their prized assets, with United reportedly interested.