Manchester United boss Sir Alex Ferguson says Patrick Vieira's attack last week was pre-planned.
Manchester City chief Vieira had a pop at United over Paul Scholes' return.
"He's an ambassador at City, so you think, 'Fine, go ahead, no problem. I've got plenty of ammunition. It won't affect me'.
"I think City will be our main challengers for a long time. Chelsea and Arsenal can stabilise themselves, and Tottenham too. They can have great teams.
"But what we've got to get used to and every Manchester United and City fan has to get used to is that there's going to be big games involving the two clubs for the next decade. It's going to be semi-finals, finals or whatever, because the two teams will be at the forefront."Ferguson said: "They maybe think they can unnerve us in some way. Patrick Vieira's column was almost programmed.