Birthday boy Kevin de Bruyne led Pep Guardiola’s side into the last four of the FA Cup and set up the mouthwatering possibility of an all-Manchester final.
De Bruyne, who turned 29 yesterday, struck from the penalty spot in the first half of a comfortable win over Newcastle as City booked a semi-final date with Arsenal.
And that means they could face United in the final at Wembley on August 1.
Ole Gunnar Solskjaer’s men take on Chelsea in their semi-final.
City dominated the opening half at St James’ Park but only had De Bruyne’s spot-kick to show for their superiority.
And Dwight Gayle missed a golden chance to level matters after the break.
That proved costly for Steve Bruce’s side as Raheem Sterling doubled the holders’ advantage almost immediately.
“We should have scored more,” said De Bruyne. “But we are happy to be going back to Wembley.
“We have had some problems with penalties this year and the gaffer asked me to step up.”
Guardiola said: “We have had some issues but Kevin has taken responsibility and he has a confident personality.
“Raheem’s finish was great and it’s good to be going to Wembley. We are struggling to focus on the Premier League but we have to prepare for the FA Cup and Champions League.”
After the disappointment of seeing their Premier League title defence formally ended by Liverpool, City remain in the hunt for another treble.
They have already won the Carabao Cup and take a 2-1 lead into the second leg of their last 16 Champions League tie with Real Madrid.
Bruce was annoyed with defender Fabian Schar, who gave away the penalty with a needless push on Gabriel Jesus.
Bruce said: “It was a blatant mistake. It was a poor challenge he did not need to make.
“But it would have been interesting if we had taken that big chance in the second half – that is what you have to do against these teams.”