The 26-year-old is keen on a move to the Premier League.
“Diamanti would like to play in the Premier League and we are in negotiations with West Ham, but the offer is not satisfactory,” Spinelli told Sky Italia.
“We also received a proposal from Parma for co-ownership worth £3m, but we value him at around £8m.
“It is not out of the question that Diamanti could remain with us, though.”