Spain boss Vicente del Bosque has insisted that his squad for next week's friendly against Italy is not a clear indication of his thinking for the World Cup.

Atletico Madrid forward Diego Costa is in the squad for the first time, but the La Roja head coach has warned the 25-year-old that he must continue to impress in the latter part of the season.

"I do not know if he (Costa) has had many pressures, I have not spoken to him since then. He has been called up and he is in the same line, that is why he has been called up. He is a singular case, he born in Brazil, has formed here and he demonstrated in his club that he should come," Del Bosque told reporters at a press conference.

"There are still three months left for the World Cup, this is not the final list, it may enter new people. The players are going to have the test in all competitions until the end of the year. The encouragement of coming to the national team will be great for them."

Costa has scored 27 goals in 35 games for his club this season.