Manchester United have been handed encouragement in their pursuit of Borussia Dortmund's Robert Lewandowsi, after the clubs chief executive admits 'economical factors' will decide his future, the Telegraph reports.

Sir Alex Ferguson has been a long term admirer of the towering Polish striker and even personally went to scout him at the Etihad Stadium in October while he was in action against Manchester City in the Champions League.

Dortmund reportedly rejected an offer for the 24-year-old from United in August, the same month that Ferguson landed Robin van Persie from Arsenal. However the United chief still seems interested in bringing the striker to Old Trafford.

With Lewandowsi rejecting Dortmund's offers of extending his current contract which expires in 2014, the clubs chief executive has admitted that the right fee could prize their star forward away from the club.

“We will have to make decisions in this case at the end of the season. We may decide on economical factors." Watzke said. The Polish international has a prolific record for Dortmund scoring 39 goals in 82 league games and it is understood that he is keen to move to the Premier League, with United his favoured destination. The Red Devils also signed currently injured Japanese international Shinji Kagawa from the German club in the last transfer window. A deal for Lewandowski in the summer looks most likely and if he was to join, he would add to an array of talented forwards at Old Trafford with Wayne Rooney, Robin van Persie, Danny Wellbeck, and Javier Hernandez already at the club.