"As European champions people are right to see us as one of the favourites but there are other powers in world football," Del Bosque told Reuters in an interview on Friday.
"In the Americas, Brazil and Argentina (are also favourites). In Europe (it is) principally England but France, Italy and Germany are up there too."
Del Bosque, speaking after announcing Spain's squad for Wednesday's friendly against France in Paris, said some of the African sides were strong too.
"Maybe they are not ready to win a World Cup but they are difficult rivals for anyone," said the 59-year-old former Real Madrid coach.
Some have expressed doubts the World Cup in South Africa in June can be staged successfully but Del Bosque said he was confident the organisation would be up to scratch.
He also said he was unconcerned about security.
"I am not worried," said Del Bosque. "They have invested a great deal, both economically and in social terms and they will make every effort to make sure everything goes marvellously."
Del Bosque recalled Fernando Torres to his squad on Friday after the Liverpool striker missed the friendlies against Argentina and Austria in November due to injury.
"He has got over his injury and made a good impression," said the coach.
"Now we must be careful not to push him too far and make sure he has the time on the pitch he needs so his return is as positive as possible."
PHYSICAL FACTOR
One of the main worries for coaches ahead of the month-long World Cup is the intensity of the European club season which could lead to players burning out or being injured, Del Bosque said.
"Of course we could see some physical problems," he said. "We know the physical factor is extremely important at a World Cup.
"That's why we have to focus on both physical and mental recuperation once the season is over."
Del Bosque took over from Luis Aragones after Spain's Euro 2008 triumph and said he planned to remain in the job as long as the Spanish soccer federation (RFEF) had confidence in him.
He said he could see Barcelona coach Pep Guardiola, who led his club to an unprecedented six trophies in 2009, taking over one day.
"But I don't think he'd be the only candidate," added Del Bosque. "Fortunately in Spain the coaching system is extremely well regarded and there are many candidates who could become coach of Spain."
His team are in World Cup Group H with Switzerland, Chile and Honduras and Spain's first match is against the Swiss on June 16 in Durban.
