Pachuca striker Enner Valencia is undergoing a medical at West Ham.
The 25-year-old scored all three of Ecuador's World Cup goals, attracting the attention of a number of Premier League suitors in the process.
It now appears that West Ham have won the race to sign Valencia - who will become manager Sam Allardyce's fifth summer signing 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 the club 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 fellow forward 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 said.
"I won't talk about prices, but if he is sold, it will be the highest transfer fee ever in Mexican football football, otherwise he won't be sold.
"We are seeking the possibility that is convenient for him and the club and that he is sold for the price that we like. We want to keep a percentage of the player in case he is sold in the future to another big team in Europe.
"It hurts me, I don't want to sell him and neither does the manager or the fans but we can't go against the career the kid aspires to."
Allardyce will be hoping that if Valencia is brought in he can prove stiff competition with Carroll for the main striker's berth in his side.
England international Carroll missed a large part of last season with a troublesome foot injury and the Hammers struggled to score goals in his absence.