Phil Foden opened the scoring before Haaland took centre stage with a second-half double, either side of an incredible miss from the Norwegian, as City bounced back from two consecutive Premier League defeats.
United went into a derby ahead of City in the Premier League table for the first time in five years.
But that owed more to City’s early season struggles than signs of progress for Amorim’s men, who have taken just four points from their opening four games and been dumped out of the League Cup by fourth-tier Grimsby.
“In these kind of games we need to be perfect and in this game we were not perfect,” said Amorim.
“The frustration is always the same because with the amount of chances (we create), we need to score goals.”
To cap a fine City display, goalkeeper Gianluigi Donnarumma marked his debut with a stunning save from Bryan Mbeumo to deny United a foothold in the game at 2-0.
City remain six points adrift of leaders Liverpool, but victory is a huge confidence boost for Pep Guardiola’s side ahead of facing Serie A champions Napoli and Premier League title rivals Arsenal next week.
“We needed this,” said Haaland. “You always want to win the derby but you could feel it extra today. I’m so relieved, so happy we managed to do it altogether. We have to keep going.”
Meanwhile, Mohamed Salah scored a stoppage-time penalty against Burnley as Liverpool maintained their perfect record to return to the top of the Premier League.
Scott Parker’s men had doggedly kept the champions at bay but a Hannibal Mejbri handball in the dying seconds gave Salah a chance to win the match and he made no mistake.
Liverpool are the first side in Premier League history to win four consecutive games with winning goals scored in the final 10 minutes or later– with Sunday’s coming in the 95th minute.
They are three points clear of Arsenal, who went top of the table on Saturday with a 3-0 win against Nottingham Forest.
Arne Slot’s Liverpool, chasing a record 21st English league title, have not been at their best this season but have found a way to win all four of their matches.
The Dutchman said his team had struggled to create clear-cut chances against a side who defended deep.
They had 27 shots at Turf Moor but just four of those were on target.
“We kept playing, we kept moving the ball around,” Slot said. “They got more and more tired which is normal when you have to defend for 80 percent of time and then we got as many attackers on as possible.”
“Difficult game but all of them are in the Premier League. A clean sheet and from open play we hardly concede a chance. That’s a good thing,” he added.
“It is normal and a lot of new players, we will get better and better but in the meantime we have 12 points.” (AFP)
