The former Bayer Leverkusen and Bayern Munich winger has been with Brazilian side FC Santos for the past year, but would be available on a free transfer at the end of the current campaign.

Dortmund, who are still fighting against relegation with five games of the season remaining, are looking to improve their side for next season and the Brazil international is one of their top targets.

"We have enquired about whether and with what conditions a transfer for Ze Roberto would become possible," said Borussia president Reinhard Rauball.

The 32-year-old enjoyed four successful years with Bayern after rising to prominence in a Leverkusen side that finished as runners-up in the Bundesliga, German Cup and Champions League in 2002.

And earlier this year he admitted he would like to try his luck in the Bundesliga again before ending his career.

"I would happily return to Germany," he said.

But Dortmund would face competition for his services, and Rauball told Sport Bild magazine the club's chances of signing Ze Roberto are "not so high".

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