Ralf Schumacher has refused to deny speculation linking him with Toro Rosso's vacant race cockpit for 2010.

The 34-year-old German, who races with Mercedes in the DTM series, has this week been back in the headlines, revealing an offer from one of F1's new teams that he turned down.

Reports said Toro Rosso, Sauber and Renault remained possibilities for a return to the sport for Schumacher, a six-time race winner who lost his Toyota seat at the end of 2007.

Red Bull-owned Toro Rosso is often billed as a team for young drivers, fielding rookies Sebastien Buemi and Jaime Alguersuari in 2009.

But while Swiss Buemi has been retained for next season, Spanish youngster Alguersuari's future is less certain.

Schumacher, who is six years younger than his famous brother, knows Toro Rosso's team principal Franz Tost well not only from their days at BMW-Williams, but from when Tost managed the German's formative career in Japan.

Austrian Tost, 53, was also employed by Ralf's former manager Willi Weber to look after the driver when he entered F1 with Jordan in 1997, and subsequently switched to Williams in 1999.

"Franz Tost and I are very good friends," Schumacher told Germany's SID news agency this week. "But it should be understood that I am not going to name any teams.

"It is all speculation," he added.

F1 chief executive Bernie Ecclestone told Bild newspaper in a new interview that it would be "good" if Ralf Schumacher returns to F1.