The Hammers are on the verge of a breakthrough in talks with the Dutch giants over a move for the Ghanian international in a move worth up to £38m.
Brighton agreed with Ajax earlier this summer but a deal broke down and the Irons look to be in a position to pounce.
Steijn, naturally, is eager to keep a player who scored 18 goals while registering seven assists last season and believes he will be available for selection up until the second leg with Ludogorets on August 31.
“It is very clear that he will be there for this two-match fixture,” he told VTBL.
“I hope he stays with us. As for the rest, that’s something on Sven (Mislintat)’s plate – in combination with potentially interested clubs. That goes beyond me. Everyone within the club and also Mo himself knows that I very much want him to stay.”