Seven-time world champion Michael Schumacher [Images] has cancelled his plans to return to Formula One because of fitness concerns, the German driver said on Tuesday.

"I really tried everything to make that temporary comeback possible, however, much to my regret it didn't work out," he said in a statement on his website (www.michael-schumacher.de).

"Unfortunately we did not manage to get a grip on the pain in the neck which occurred after the private F1-day in Mugello, even if medically or therapeutically we tried everything possible."

Schumacher, 40, had been expected to drive for Ferrari [Images] at the European Grand Prix [Images] at Valencia on Aug. 23, standing in for Felipe Massa [Images] as the Brazilian recovers from a fractured skull.

The German retired at the end of the 2006 season.

Since then, he has raced occasionally in a motorcycling series but was injured in a crash in February.

"The consequences of the injuries caused by the bike accident in February, fractures in the area of head and neck, unfortunately have turned out to be still too severe," Schumacher said.

"That is why my neck cannot stand the extreme stresses caused by Formula One yet.

"I really tried everything to make that temporary comeback possible. However, much to my regret it didn't work out," he added.

The German won 91 races in 250 starts.

"I am disappointed to the core. I am awfully sorry for the guys of Ferrari and for all the fans which crossed fingers for me," Schumacher said. 

"All I can do now is to keep my fingers crossed for the whole team for the coming races." 

Schumacher's statement did not say who Ferrari might turn to as a driver instead. 

Last week Schumacher said he was slimming down for the race, but complained of some neck pain. 

"I only have to admit that my neck pinches a bit. We have to get a grip on that as health has priority - that's the clear arrangement made with Ferrari and, by the way, with my wife, too," Schumacher said.

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