And Sterling then secured our ticket into the last four with a sublime finish midway through the second half.
It was our 10th consecutive win in the competition and the reward for the FA Cup holders is a semi-final assignment with Arsenal at Wembley next month.
Having made four changes from the side which lost 2-1 at Chelsea last Thursday, Guardiola had spoken beforehand of his desire and determination to lead City a step closer towards defending the FA Cup crown.
His strong selection was ample proof of the manager’s intent and City made our intentions crystal clear in a dominant first 45 minutes with the Magpies constantly pegged back and stretched to the limit by our fluidity and tactical flexibility.
With City quick, incisive, and hungry on the ball, wave after wave of City attacks rained down with Newcastle having to soak up up constant pressure.
City’s dominance was almost rewarded on 12 minutes.
Kevin De Bruyne – who produced a sublime display on his 29th birthday – despatched a wonderful pass to David Silva on the left edge of the box, the skipper rolled the ball invitingly back to the unmarked Riyad Mahrez but the Algerian’s snapshot was just too high.
Five minutes later, City were inches away from opening our account, Gabriel Jesus’s instinctive flick from a powerful Kyle Walker cross bouncing ricocheting agonisingly wide of the target and the pressure continued with a fine curling Mahrez shot again mere inches away.
And only two smart saves from Newcastle keeper Karl Darlow denied Raheem Sterling as he kept out a close-range lob and 16-yard shot in quick succession.
However, our dominance was finally rewarded on 37 minutes and, fittingly enough, it was birthday boy De Bruyne who made the all-important break through from the penalty spot.
Newcastle came out with more purpose and endeavour thanks to a tactical tweak at the break – but Mahrez was still an ace away with a superb 52nd minute power drive.
The Magpies though proved far more threatening opponents and should have drawn level on 65 minutes.
A mispass from Otamendi only found Saint-Maximin and the Frenchman’s pinpoint cross from the right found unmarked substitute who blazed over the bar from six yards.
Within 60 seconds City made Newcastle pay the price.
The England star cut inside before curling home a brilliant right foot shot to all but seal the deal.
Many happy returns
Kevin De Bruyne has been in imperious form since the resumption of action and the Belgian was at his peerless best at St James’ Park.
Celebrating his 29th birthday, De Bryune was absolutely everywhere and marked another dominant display by coolly despatching a 37th minute penalty for his 12th goal of the season and third in the past four games.
The victory was the perfect present for De Bruyne – along with every City fan - and was his 100th club career goal across all competitions.
Man of the match
Raheem Sterling: A sublime goal capped another fine performance from the City and England talisman and only tow fine saves from Newcastle keeper Karl Darlow prevented Raz from claiming a hat-trick.
“We are in the semi-finals.
“It was not easy to attack against a team defending so deep but it was a good performance.
I am happy to go back to London, to Wembley.
What it means
City can now look forward to a mouth-watering FA Cup semi-final encounter at Wembley against Arsenal.
Sunday’s semi-final draw also pitted Manchester United with Chelsea.
Both ties will take place at Wembley over the weekend of July 18/19.
City are back in Premier League action this Thursday evening when newly-crowned champions Liverpool visit the Etihad Stadium.
Guardiola’s side will be keen to not only to lay down a marker ahead of next term but also to return to winning ways in the league after last Thursday’s loss away at Chelsea and so help strengthen our grip on second spot.
Kick-off for what should be an intriguing clash at the Etihad is 8.15pm.
City: Bravo, Walker (Cancelo 70), Mendy, Laporte, Otamendi, Gundogan, De Bruyne (Rodrigo 70), D Silva (c) (Bernardo 64), Sterling, Jesus, Mahrez (Foden 64)
Subs: Ederson, Stones, Zinchenko, Sane, Harwood-Bellis
Newcastle: Darlow, Manquillo, Schar, Lascelles, Fernandez, Rose, Saint-Maximin, Hayden, S Longstaff, Almiron (Gayle 64), Carroll (Joelinton 64)
Subs: Dubravka, Shelvey, Muto, Krafth, Yedlin, Lazaro, M Longstaff