Premier League clubs are on red alert with Robert Lewandowski's future at Borussia Dortmund thrown into doubt. The Mirror says Manchester United were willing to pay £16m for Lewandowski in the summer.

Their interest cooled in Lewandowski, 24, once they signed Robin van Persie.

But Sir Alex Ferguson remains a long-term admirer and wants to be kept informed of the stand-off. Chelsea, Tottenham and Manchester City are also watching developments.

The German champions fear losing their star man for nothing and could be ready to cash-in.

Dortmund chief executive Aki Watzke said: "We will sit down and discuss what to do next if Robert does not extend his contact."