Manchester United have been alerted after Schalke admitted Klaas-Jan Huntelaar has a buy-out clause of 20 million Euros ($25 million).

Huntelaar has been in terrific form for his club, scoring 31 goals in 34 appearances last season in the Bundesliga. Manchester United have been heavily linked with the prolific Dutchman in the past and could now be open to a move after losing out on Robert Lewandowski.

Borussia Dortmund, recently said Lewandowski was not for sale, ending any chances of United signing the Poland striker.

Huntelaar, despite underwhelming spells with Real Madrid and AC Milan, has scored goals wherever he has played and will be a great addition to United's squad as Sir Alex Ferguson looks to find the perfect foil for Wayne Rooney.

Huntelaar, 28, has been monitored by Arsenal and Tottenham previously, and the Dutchman will jump at the chance of playing in the English Premier League.

Schalke general manager Horst Heldt admitted Huntelaar, who has just one year remaining on his current deal with the German club, has a buy-out clause and could leave if a suitable offer was made. "Huntelaar does have a €20 million buyout clause, and the rich clubs can afford it," Heldt told German newspaper Bild.

"But Klaas-Jan has always stressed that he wants to be a champion. This he can be only with Real (Madrid) or Barcelona in Spain.

"I do not think he wants to go there. What would he do there? Since nothing more than the weather is better."