Pep Guardiola has given Manchester United hope of a revival under new minority owner Sir Jim Ratcliffe by saying that Manchester City's era of dominance won't last forever.
United have gone more than 10 years without winning the Premier League title while City, under Guardiola, have lifted the trophy in five of the last six years.
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Ratcliffe has laid out his plan to "knock City off their perch" within three years and, ahead of the 192nd Manchester derby at the Etihad Stadium on Sunday, Guardiola has said it might be possible.
"In the 80s it was Liverpool, in the 90s it was United and now we have won seven Premier Leagues in the last 11 or 12 years," Guardiola told a news conference on Friday.
"In 50 or 60 years, there has never been one country where one team dominates and controls everything but we try to extend this as much as possible for many years."
United have struggled since Sir Alex Ferguson retired in 2013, going through a string of managers including David Moyes, Louis van Gaal, Jose Mourinho and Ole Gunnar Solskjaer, but winning just four trophies.
Erik ten Hag, who lifted the Carabao Cup last season, is under pressure after a poor campaign and Guardiola said he has sympathy with the challenge facing the Dutchman at Old Trafford.
"I would say at big clubs you have to win and win," Guardiola said. "Not just United, you have to win in the big clubs. It's not easy for United to come from an incredibly successful period with Sir Alex and cope with that, that is not easy. Sometimes I can understand it.
"Before in England, with the managers they had more patience. Today everyone has a lot of pressure. But the diagnosis [of United] like I said before I don't know the reason why [they have not been successful]. I am not there."