The Scot used a news conference to fire back at City's former player Patrick Vieira for saying earlier in the week that United had shown their weakness in bringing Paul Scholes out of retirement.
"If it's desperation bringing the best midfielder in Britain for the last 20 years back then I think we can accept that," said Ferguson.
"[City manager] Roberto [Mancini] had a wee dig a couple of weeks back. We're all going to play our hand that way. There will be plenty of ammunition for that," he added.
"If you talk about desperation, they played a player the other night who refused to go on the pitch and the manager said he'd never play again and he takes a five-month holiday in Argentina.
"What is that? Could that come under the description of desperation? There will be plenty of ammunition don't worry," smiled Ferguson.
Vieira, now City's football development executive after a long career with Arsenal, had said Scholes' return "shows a little bit of weakness in United, because they had to bring a player back who was 37.
"With all the respect I have for Scholes, him coming back shows that they don't have talent in there to replace him," added the Frenchman.
"We want him to stay because we think he's going to be a fantastic Manchester United player. We hope that's the case," said the Scot.
