With the European Champions' League transfer deadline just around the corner on Thursday, the deal would have to be completed by then if United wished to use him in that competition.
Paolo is all set to line up in West Ham's team when they face Chelsea again tomorrow, and he is certainly in Glenn's plans for the match.
Glenn told the official site of his frustration with the whole saga: "It is a difficult one to call and we hope he will still be with us, but we'll just have to wait and see.
"To be honest, as a manager of a player of that talent you'd want him to stay and play for you. But I've maintained all along this is not an ordinary club that has come calling for his services - it is, after all, Manchester United, probably the biggest club in the world, and it would be difficult to stop any player going there.
"But I've been saying this for two or three weeks and I end up sounding like an old record. We all want the speculation to end one way or another and I include Paolo in that. It must be difficult for him because we keep talking about ourselves, the club, but sometimes people forget to mention the person who is the centre of attention. I just feel next Thursday is the critical day."