Alvarez whipped home what proved to be the winner after 31 minutes of what was a tight contest, though Erling Haaland squandered a couple of chances to make the margin of victory greater as United struggled to carve out many clear-cut chances at the Etihad Stadium.

Eddie Howe had named an unchanged side for the clash with Pep Guardiola's men, opting to stick with the same team that beat Aston Villa 5-1 last weekend, with Harvey Barnes - who registered a goal and assist in a cameo off the bench last Saturday - made to wait for his first start in black and white.

But a cagey opening saw the visitors make a few promising breaks. Anthony Gordon's low centre across the face of goal caused some problems and Joelinton had a shot charged down, but real chances were at a premium early on. City, predictably, saw plenty of the ball and had a few blocked efforts of their own: Jack Grealish and Mateo Kovacic both tried their luck to no avail.

But on the half hour, the champions moved in front with a superbly-taken goal. Alvarez took a Phil Foden lay-off in his stride and sent a terrific, powerful strike beyond the reach of Nick Pope and into the top left-hand corner from just inside the 18-yard box.

Erling Haaland, who had been well contained by centre backs Fabian Schär and Sven Botman for most of the first period, rolled a shot just past the upright in the half's later exchanges and United may feel they could have gone in level, had Gordon not been caught in two minds when a cross dropped at his feet at the far post.

Newcastle came out fighting after the restart. Gordon saw his shot inadvertently hit Joelinton and then scooped over after turning Kyle Walker moments later as Howe's men registered their intent, but a Haaland snapshot - held by Pope - highlighted the hosts' latent threat.

With Barnes on for the yellow-carded Gordon and Sean Longstaff replacing the limping Joelinton, United looked for a leveller but another well-crafted City break almost led to a second. Haaland again pulled the trigger at the end of it, but he didn't get hold of his shot and it trickled wide, just a few minutes before he forced Pope to save his low strike with his legs.

Barnes tested Ederson from range inside the final 20 minutes as the contest became stretched, but City held firm to keep the Magpies' attack at bay, limiting their openings in the final third as Newcastle tasted defeat for the first time in the new season.