Chelsea manager Jose Mourinho thinks an "old-fashioned mentality" in English football is preventing Manchester United selling Wayne Rooney.
Mourinho has been keen to sign the England international over the close-season, although a fee has yet to be agreed.
The former Real Madrid boss feels it is tradition in England not to sell to clubs in the same league and says this is what has held the transfer back so far.
"I don't think the old-fashioned mentality of 'I don't sell players to the clubs in the same country' helps the market," he said.
"It doesn't help the players and sometimes you push players abroad when you should be interested in making sure they play in your league.
"When you keep players in your league, you are contributing to making your league the best. So when you want to sell and you push the players abroad, I think you are giving the wrong contribution to the league."
Both sides won their opening Premier League fixtures, with Chelsea also beating Aston Villa on Wednesday, and the sides meet at Old Trafford on Monday.
Mourinho insists his comments on wanting to sign Rooney are genuine and not simply mind games or an attempt at destabilising David Moyes' plans ahead of Monday's clash.
"I don't understand those theories because it is normal that we would want to strengthen our squad in every position," he continued.
"It is basic and normal, and we want to give more quality to the whole structure. It is obvious that the striker position was a position we would try to improve."