Jarrod Bowen has completed his medical with West Ham ahead of a £25m move from Hull and will now meet David Moyes at the London Stadium.
The two clubs agreed a deal overnight on Thursday and personal terms have already been agreed.
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West Ham will pay an initial £18m for the forward, with up to £7m in potential add-ons.
Crystal Palace - who were Bowen's initial preferred destination - are now concentrating on other targets, with Bournemouth's Jordon Ibe an option if he is allowed to leave the Vitality Stadium.
The Eagles had been in talks to sign the 23-year-old for a deal worth £16m plus add-ons, with Newcastle and a host of Championship clubs also interested.
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Hull have already made moves on the market to find a replacement for Bowen, with Peterborough winger Marcus Maddison joining the Tigers on loan until the end of the season.
Bowen is out of contract at the end of the season and opted to not to accept a contract offer from the Humberside club earlier this month.
The Hull winger is the third top goalscorer in the Championship this season with 16 goals, two behind Brentford forward Ollie Watkins and Fulham striker Aleksandar Mitrovic.
'Bowen could make West Ham difference'
West Ham manager David Moyes believes Bowen could make a difference, but has also urged patience should the player join from Hull.
"We're always interested in players who can score goals and people who can make a difference and he can certainly do that," Moyes said.
"He's done it for Hull over several years, not just one season, and if you score goals in the Championship it gives you a good chance to score them in the Premier League.
"I've taken the likes of Leighton Baines, Phil Jagielka, Joleon Lescott and Tim Cahill from the Championship over the years.
"They don't all make the step up immediately but given time and the chance to settle and get up to speed of the game, what is expected in the Premier League then I think he could be a big success."