Schalke 04 chairman Clemens Tonnies has confirmed reports that the club are interested in signing Tottenham Hotspur midfielder Rafael van der Vaart.

The Bundesliga outfit, who have also been linked with forwards Salomon Kalou, Eljero Elia and Cacau, are looking to bolster their attacking options this summer following the departure of former Real Madrid striker Raul.

"Van der Vaart is good, but I have to admit this would be a complicated transfer," the Schalke chairman told Sport 1.

The Dutch international, 29, refused to rule out leaving White Hart Lane earlier this week.