Ferrari had the highest top speed in qualifying at the Bahrain Grand Prix, and subsequently locked out the front row. However, Mercedes responded brilliantly - albeit a tad fortuitously - to complete a successive one-two finish.
Teams are only permitted to use three complete power units per an F1 season, something that the world champion believes makes it more difficult for Mercedes to catch Ferrari's straight-line speed up.
"On the engine side of things, it's very hard to make big gains without taking risks," the five-time world champion said. "Especially with the regulations that we have these days with the amount of engines and turbos. Those steps are harder to come by.
"It's probably a combination of a couple of things. But closing that gap in the straight speed is not something that you'll see close up particularly quickly."
As a result, Hamilton doubts the Silver Arrows will be significantly closer to Scuderia in China at the weekend: "I don't know whether we will make many improvements here.
"We've not brought particularly any upgrades or anything like that, so you're not going to see a big difference. Coming into this weekend, it should be quite similar to the previous weekend."