"The transfer window is coming up and we will strengthen if we can. But the ones we like and know are difficult to get. It's difficult to prise the people we've identified away and I do fear that we won't be able to bring anybody in," he said.
"The guy coming in would have to be considerably better than the players we've got and that is hard to find.
"We're not going to waste money on someone who is not better than the defenders we've already got. We need a top international class centre-half with leadership qualities who can command the back four.
"But look what Manchester United had to do to get a top centre-back. They had to spend £28m on Rio Ferdinand. That is what it took them and they have a scouting network the same as ours but still spent that amount of money. We don't have £28m to spend.
"Money's tight now and even clubs with money are wanting to keep it. I think you will find that there will be no big transfers taking place and that most players will move on loans.
"If that's the case then you are talking about more foreign players coming into the country because, with respect, I don't think there's much in the First, Second or Third Divisions that will enhance the Premiership."
Meanwhile the Daily Express has claimed that United have been offered Dynamo Kyiv defenders Andrei Husin and Tiberiu Ghioane, as the Ukrainian club seek to clear their crippling debts.