Bayer Leverkusen cannot compete with Manchester United over Rene Adler signature - Rudi Voeller

Former Germany boss Rudi Voeller has admitted his concern that Bayer Leverkusen will be unable to extend the contract of goalkeeper Rene Adler should Manchester Unted lodge a serious offer.

The player's contract - rumoured to include a clause that allows the 18-times Premier League winners to purchase the player for a fee in excess of £20 million - expires in 2012, but Voeller, director of sport at the German club, hopes that Champions League qualification could encourage the highly rated stopper to commit to a new contract.

"We will of course try to extend [Adler's contract] - within our means," said Voeller to Kicker.

"We know that for Rene, from a sporting perspective, whether we play internationally is important. Of course we want to play in the Champions League, and this is indeed the goal of Rene."

However, Voeller admitted: "We cannot keep up with Manchester United."

Leverkusen's hopes of clinging on to the player may rest on United looking elsewhere for a replacement for veteran Edwin Van der Sar.

"Rene is not the only goalkeeper that [Manchester United] have observed," said Voeller. "We stand in good conversation with Rene and his advisers."

In addition to the 25-year-old Adler, United have been linked with Pepe Reina, Manuel Neuer, David de Gea and Maarten Stekelenburg.

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