The 29-year-old has signed a three-year deal with the Hammers, having spent the last two seasons with the Gunners. "I am always aiming as high as I can and if we can put West Ham in the Champions League why not?"
West Ham director of football Mario Husillos is confident Perez will prove another valuable addition.
'I made a decision to come here because, first, it is the Premier League, second, it's a attractive club and the fans are always helping the club and, third, for me it's an unbelievable opportunity and an awesome project the club are leading, being ambitious and keen to achieve good things.More news: 1200 tourists being evacuated from Indonesia quake islands: disaster agency
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"I'm very happy to be here at such an historic club", he said in a statement on West Ham's website.
However, in that time he did show flashes of the form that had earned him the move, accruing seven goals and five assists across competitions.
"In Spain there are also interest from some clubs, but they are not willing to assume the transfer".
West Ham opens the season with a tricky clash against Liverpool on August 12th at the London Stadium.
"His style is different from the other strikers we have available to us, and that gives the manager more options for our attacking play".