The Liverpool forward had an operation on his right knee last month, and after a medical check up with the national team on Monday was included in Spain coach Vicente del Bosque's preliminary 30-man squad.
"At the moment, we cannot say if Fernando will be ready in time for the first game of the finals, but we are optimistic," Spain doctor Juan Jose Garcia Cota was quoted as saying in the local media on Wednesday.
"He has started to work outside and is still doing gym work to improve the muscle tone around the operated knee.
"He will be here (in Vigo, north-west Spain) until the squad meet up for the World Cup finals."
Torres, who scored Spain's winner against Germany in the Euro 2008 final, forms half of a lethal attacking partnership with Valencia's David Villa.
Spain kick off against Switzerland in Durban on June 16 and go on to play Honduras and then Chile in Group H.
Thank you for reading 5 articles this month* Join now for unlimited access
Enjoy your first month for just £1 / $1 / €1
*Read 5 free articles per month without a subscription
Join now for unlimited access
Try first month for just £1 / $1 / €1
Get the best features, fun and footballing frolics straight to your inbox every week.
Thank you for signing up to Four Four Two. You will receive a verification email shortly.
There was a problem. Please refresh the page and try again.