* Costa in squad for this month's friendlies
* Alonso returns after injury, Xavi rested (Adds details, quotes, byline)
By Iain Rogers
MADRID, Nov 7 (Reuters) - Spain coach Vicente del Bosque has called Atletico Madrid's Brazil-born forward Diego Costa into his squad for the first time for this month's friendlies away to Equatorial Guinea and South Africa.
Top scorer in La Liga with 13 goals in 12 appearances this season, Costa signed a formal letter last month stating his wish to play for his adopted country and ending a tug-of-war between the world and European champions and Brazil over the 25-year-old.
"He has fulfilled all the requirements to play for Spain and he is on very good form," Del Bosque told a news conference on Thursday at the Spanish soccer federation (RFEF) headquarters outside Madrid.
"I have absolutely no doubt that he will be a squad member like any other," he added.
"The last step in the process was to get to know him personally and he left us with a magnificent impression."
Costa's commitment to Spain angered Del Bosque's Brazil counterpart Luiz Felipe Scolari, who withdrew the player's invitation to play in this month's friendlies against Honduras and Chile and accused Costa of "turning his back on the dream of millions".
He represented Brazil in friendlies against Russia and Italy in March but was left out of the squad for June's Confederations Cup and is not tied to one country until he has played in an official competitive game.
He is the fifth Brazilian-born player to be included in a Spain squad following Heraldo Becerra, Catanha, Donato and most recently Marcos Senna.
Costa's first chance to feature could come on Nov. 16 when they play Equatorial Guinea in the West African nation's capital Malabo.
They then travel to play South Africa at Soccer City in Johannesburg, scene of their maiden World Cup triumph in 2010.
Del Bosque dismissed a suggestion Costa would not be as committed to Spain as someone born there and said he was not concerned about a possible backlash at next year's World Cup finals in Brazil.
Costa would fit seamlessly into the Spain side and link up well with their creative midfielders like Xavi and Andres Iniesta, he predicted.
"We have intelligent players who are capable of adapting to the characteristics of any team mate," Del Bosque said.
"I don't think that anyone would struggle to fit into our playing system.
"I expect that a player that fights like Diego with such energy, a player with the quality he has on and off the ball, to be a positive addition.
"We have midfielders who understand football perfectly and for sure they will have a player who offers himself constantly and give them a lot of options in attack.
"I think he will fit in without any trouble just like all the other players we have called up."
Tall and powerful in the air, Costa has excellent touch and vision and is a handful for defences who find it tough to cope with his physical approach.
He will give Del Bosque, who often plays without a traditional centre forward, an extra option up front and will likely compete for a place in the starting lineup with Manchester City forward Alvaro Negredo.
Real Madrid midfielder Xabi Alonso returned to the squad for the first time since a five-month injury layoff, while playmaker Xavi was rested and his Barcelona team mate Gerard Pique, a centre back, misses out after picking up a groin problem in Wednesday's Champions League game against AC Milan.
Goalkeeper: Iker Casillas (Real Madrid), Pepe Reina (Napoli), Victor Valdes (Barcelona)
Defenders: Alvaro Arbeloa (Real Madrid), Raul Albiol (Napoli), Sergio Ramos (Real Madrid), Alberto Moreno (Sevilla), Juanfran (Atletico Madrid), Javi Martinez (Bayern Munich), Inigo Martinez (Real Sociedad), Nacho Monreal (Arsenal)
Midfielders: Sergio Busquets (Barcelona), Xabi Alonso (Real Madrid), Koke (Atletico Madrid), Andres Iniesta (Barcelona), Santi Cazorla (Arsenal), Cesc Fabregas (Barcelona)
Forwards: Jesus Navas (Manchester City), Alvaro Negredo (Manchester City), Pedro (Barcelona), David Villa (Atletico Madrid), Juan Mata (Chelsea), Diego Costa (Atletico Madrid) (Editing by Ed Osmond and Justin Palmer)