Formula One commercial rights boss Bernie Ecclestone said Tuesday he believes German Red Bull driver Sebastian Vettel rather than compatriot Michael Schumacher could be the next world champion.

Seven-time world champion Schumacher, who turns 41 on January 3, stunned Formula One by coming out of retirement to sign a three-year, 30-million-dollar deal with Mercedes, a decision expected to spark a surge of interest in the sport in 2010.

"I'm saying it well in advance, but for me, Sebastian Vettel will be the next world champion," Ecclestone told the daily Bild on Tuesday.

Vettel, 22, finished second last season with four wins.

"Michael Schumacher will have many rivals such as (Lewis) Hamilton, (Fernando) Alonso and above all Vettel," said Ecclestone, who admitted he was "very, very happy" with Schumacher's return.

"Next season there will be four former world champions on the starting grid with Alonso, Hamilton, (Jenson) Button and Schumacher. I don't remember the last time we had such a line-up," he said.

"Of course Schumacher can claim an eighth world title, but five other drivers can target this title. In the end it will come to the one with the best car."

Meanwhile, Schumacher's younger brother Ralf Schumacher revealed he too was considering a return to Formula One.

Ralf Schumacher, who competed from 1997 to 2007, said he had received an offer from a team to compete in the 2010 world championship.

"My passion for F1 is still burning exactly like my brother described when announcing his return," said the 34-year-old Schumacher.

"I'll only seriously consider a return if it's for a competitive stable," added the younger Schumacher, who won six Grand Prix races during his career with Jordan (1997-98), Williams (1999-2004) and Toyota (2005-07).

Ralf Schumacher could interest the Renault and Toro Rosso teams, who are on the look out for a second driver.