The Socceroos defender recently rejected a new deal from the Hammers believed to be in the vicinity of $60,000 a week.
A source in Turkey says the deal is imminent.
"The fact that Harry Kewell is there and Johan Neeskens (former Australia assistant) also is a big plus for him and quite significant," the source said.
"Lucas Neill will get a shock at just how big the club is when he arrives here.
"There's a fan base of over 20 million and they are fanatics. He will be widely appreciated."