West Ham have had a £29m offer for striker Maxi Gomez accepted by Celta Vigo, Sky Sports News understands.
Valencia are also understood to have had the same offer accepted by their La Liga rivals, which includes add-ons.
The 22-year-old has been a target for the Hammers since last summer, and extensive talks were also held in January but the Spanish club wanted his £43.3m release clause met.
Manuel Pellegrini has revived his interest again this summer and is moving closer to making Gomez his fourth signing of the summer, having already completed the captures of attacking-midfielder Pablo Fornals from Villarreal and two goalkeepers; David Martin and Roberto Gago.
West Ham could also soon complete a fifth signing - and fourth from Spain - after launching a £13m offer for Eibar's defensive-midfielder Joan Jordan.
They had been trying to sign Barcelona's Andre Gomes, but he is understood to prefer a move back to Everton, while the Hammers are also one of the clubs keen on a permanent deal for Nathaniel Clyne.