"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.
"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."
"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."
"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.
"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.
