The Velez Sarsfield striker has arrived in England and will reportedly sign a three-year deal at Upton Park.
For Zarate, the move would represent a second chance in England's top flight, after he enjoyed a loan spell at Birmingham City in the second half of the 2007-08 season.
Since then, the Argentinian has played for Lazio and Inter in Serie A, before returning to first club Velez in his homeland last July.
The 27-year-old is now looking forward to linking up with West Ham and attempting to make a name for himself in the Premier League.
Speaking to Sky Sports News, he said: "It's a new chance for me. West Ham called me. They are a fierce team and now I think I want to play (there)."
Fellow countrymen Carlos Tevez and Javier Mascherano have previously plied their trade at Upton Park, and Zarate confirmed he had briefly spoken to the duo.
He added: "Yes (I have spoken to them) a little bit. Now we will talk (with West Ham's owners) and maybe I will sign."
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