Diego Costa could be set to miss the FIFA World Cup as Spain coach Vicente del Bosque admitted uncertainty over the star striker.

The Atletico Madrid striker's torn hamstring saw Del Bosque delay finalising his 23-man squad and he may wait until the FIFA deadline on June 2.

But, despite optimism earlier in the week, Del Bosque has questioned whether Costa will be fit for the reigning world and European champions.

"I'm not sure Costa will make it," Del Bosque said.

Even if Costa misses, Spain have plenty of attacking talent, with Fernando Torres, David Villa, Fernando Llorente and Alvaro Negredo among their other striking options.

Del Bosque said there was still time for Costa to recover, but wants the 25-year-old at his fittest.

"We've still got time but now it's in the hands of the doctors and the medical team. We have to be cautious," he said.