Chelsea striker Diego Costa has insisted that there will be "no lack of effort" in trying to improve his goalscoring form for Spain.
The Brazilian-born player has managed to strike just once for the nation after making his debut last year.
In Tuesday night's 1-0 win over Macedonia, Costa had another frustrating run-out.
"I've got a lot to improve and I've got to start scoring goals," Costa told AS. "There will be no lack of effort on my part.
"I am always filled with ambition whenever I get called for the national team. On a personal level I am not happy because I didn't manage to score tonight although I'm happy with the victory."
At club level, during his first season at Chelsea, Costa netted 20 goals in 29 appearances.
