"It hasn't moved forward in the last 48 hours," Brown told the Hull Daily Mail.
"He has an offer from us and an offer from Celtic and someone has said something about West Ham.
"That is news to us but if so, so be it. We are now in a three-horse race as opposed to a two-horse race.
"We are confident we are still in the pole position but these things are always a concern when they are not done and dusted.
"If there is not a decision in the next 24 or 48 hours we are going to have to move on to other players."