Pachuca striker Enner Valencia is undergoing a medical at West Ham, Press Association Sport has reported.
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Valencia, 25, scored all three of Ecuador's World Cup goals, attracting the attention of a number of Premier League clubs.
It now appears West Ham have won the race to sign him -- and he will become manager Sam Allardyce's fifth acquisition of the summer if the deal is completed following the medical.
Although any fee is likely to remain undisclosed, Pachuca chairman Jesus Martinez has insisted Valencia will not be allowed to leave for anything less than a Mexican league record.
It has been reported the Hammers would pay a fee close to the club-record total paid for Andy Carroll last summer and Martinez was quoted last week as saying he wants any deal to include clauses that would see Pachuca benefit if Valencia was to move on.
"There are various offers for Enner Valencia: the strongest and closest to what the player and us are demanding is from a club from England," he told Ecuagol.
"I won't talk about prices, but if he is sold it will be the highest transfer fee ever in Mexican football -- otherwise he won't be sold.
"We want to keep a percentage of the player in case he is sold in the future to another big team in Europe."
Martinez said he did not want to sell Valencia, "but we can't go against the career the kid aspires to."