"I think he's going to give one or two of them a driving lesson," the F1 supremo told a news conference.

The 40-year-old German is poised to return to the track at the European Grand Prix in Valencia on Aug. 23 in place of Ferrari's injured driver Felipe Massa.

The Brazilian is recovering from a fractured skull after being hit by a bouncing spring before crashing during qualifying for the Hungary Grand Prix last month.

"He obviously wouldn't have decided to come back unless he thought he was going to be competitive and Michael is a competitive guy," Ecclestone added.

The surprise return of F1's most successful driver, who retired at the end of 2006, has been hailed by motor sport fans and will provide intrigue ahead of the race in Spain.

His comeback will see McLaren's current world champion Lewis Hamilton, as well as Red Bull's title contender Sebastien Vettel -- nicknamed 'Baby Schumi' by his compatriots -- race for the first time against the man who dominated the sport for a decade.

"He's always been super popular even though he won too many races and people said he was boring. He was never boring and he won't be boring now," Ecclestone said.

"I think I was just as surprised as Willi Weber - his manager - he didn't know he was coming back (either). I think it was (Ferrari president) Luca di Montezemolo that convinced him."

Schumacher's preparations were hampered on Monday by the Red Bull and Williams teams who have opposed Ferrari's request to let the German test in Massa's F60 car prior to Valencia.

Formula One regulations do not allow track testing during the season, although Schumacher completed 70 laps in a 2007 version Ferrari at Mugello near Florence last Friday.