The Red Devils have already had two bids for the Spain midfielder rejected by the Catalans and Moyes is in the dark as to whether the Premier League champions will up their offer or train their targets elsewhere.
The Scot said: "I couldn't tell you if there will be another bid. Obviously we will take stock of it and consider what we are going to do next.
"I never at any time said I knew we would get him. I just said we had made offers.
"But what we have here is a really good squad of players already. You mustn't forget about the quality that is already here at Manchester United.
"Undoubtedly we are hoping to add to it. I am quite confident we will do, certainly before the window shuts."
United have already missed out on one long-time target from Barcelona over the summer - promising midfielder Thiago Alcantara opted to join European champions Bayern Munich in a 25m euro deal.