West Ham have been chasing Arnautovic for weeks but Stoke were keen to keep their star.
The BBC claim two bids for Arnautovic, 28, were snubbed by Mark Hughes’ Stoke.
The first was a £15m offer.
Express Sport understands Hughes was then furious when the Austrian indicated he wanted to leave.
And the Potters have since wasted little time keeping onto the winger, who will now have a medical at West Ham.