Slow-starting McLaren dramatically slashed the gap to Aston Martin since the summer break thanks to an impressive string of podiums over the past four races, while the Silverstone-based squad has generally struggled since the summer.
Norris' latest runner-up spot in last weekend's US Grand Prix was enough for McLaren to leapfrog Aston Martin and hold fourth by six points.
Norris said he was puzzled by how Aston was making its car "slower and slower" in recent weeks and thinks McLaren can still target Ferrari, which is 80 points clear in third.
"It's our target," he said about Ferrari's lead. "I think we're in a good rhythm.
"It's been clear that Aston… I don't know, they seem to have managed to make the car slower and slower with every upgrade that they’ve bought.
"They were racing [Red Bull] at the beginning of the year and they were out in Q1 and then they've been struggling, so I don't know what their issues are."
Aston's Fernando Alonso took six podiums in the first seven grands prix but has only managed to add one top-three finish - second place in the Dutch GP, since then.
Norris has pulled off the opposite thanks to a dramatic in-season turnaround by McLaren, who produced powerful upgrades before the summer break and then again at Singapore.
"They were very strong, they had a lot of points in the first half of the season and in the second half they've been struggling, and for us, it’s vice versa," he added, having taken six podiums since the British GP.
In the first eight races, McLaren had only managed to score 17 points between Norris and rookie team-mate Oscar Piastri, and it is that unlikely comeback that has made it easier for the Briton to settle for podiums as his wait for a maiden win continues after 100 races with McLaren.
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"When you look at where we were, how bad Bahrain was for us, how many seconds off pole we were, my six pitstops in the first race of the season, I lost my PU straight away… there are things that put us on the back foot from the beginning," Norris explained.
"And when you look at where we are now, to be fighting against a Red Bull, which was an unrealistic target for almost anyone, and fighting against a Mercedes…
"As much as we are disappointed that we can’t go for a race win, when you put it in perspective of where we were and how much we've improved, I think it's still an amazing day for us."
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