Chelsea striker Diego Costa has admitted that he is frustrated by his failure to string a number of international appearances together.

The 26-year-old is widely regarded as one of the deadliest strikers in Europe, but he has made just seven appearances and scored only one goal since choosing to represent Spain ahead of Brazil.

Costa, who missed a Spain double-header in November, will again be absent from Vicente del Bosque's side for the next two games due to a hamstring injury, and he conceded that his injury problems 'bother' him.

"I was in good form, I thought everything was finally going to work out. You always arrive [to the national team] with some aches. But this time, I would have arrived without any pain. I really wanted to prove my form and my worth... but again [injury] happened," Costa told Marca.

"My history with the national team is that it still hasn't really started. I haven't done anything yet. The national team is something I think of. I am sorry that I cannot bring what I would like to. Something always happens when I get close to playing for Spain. It bothers me from a personal standpoint but I hope this will end. I've gone through a lot to be in the national team and I hope good times will come. I am looking to succeed with Spain. The national coach and my teammates are counting on me.

"They deserve to be paid back for the confidence that they placed in me. I hope I can do that on and off the pitch. Sometimes it angers me that they put in doubt my commitment. I already proved that I'm enthusiastic and that I want to achieve success with the national team. The best way to silence the critics is to play and to do things well. But I haven't done that yet and hence, I have to listen and swallow. It is one thing is to criticise my performance, which is fair, but another to criticise my commitment."

Spain will face Ukraine in a Euro 2016 qualifier on Friday before taking on the Netherlands in a friendly four days later.