Fernando Alonso expects Mercedes' domination of Formula One to continue in 2016, but believes McLaren has the potential to develop the best chassis on the grid by the European season.

Mercedes is chasing a third world title this year while McLaren is looking for a return to respectability after a lack of reliability and performance from its Honda power unit in 2015. Alonso is not expecting any change at the top, but suggested McLaren could have the best car by the Spanish Grand Prix in May if engine performance is removed from the equation.

"I think Mercedes' domination has not finished and they are very, very strong," Alonso said. "There have been some interesting days in testing at the first two days, but with that amount of laps [Mercedes completed 156 laps on the first day and 172 on day two] it means you have very clear things to learn. When they put the potential on the car as well it means they will be stronger than ever probably, more than the last two years.

"I think to win is not an easy task [for McLaren], but I'm very proud of the team and of what we achieved in the last couple of months. I think the target of having the best car, the best chassis is reachable and very possible by the European races and motivation is very high. There is not a magic solution or crystal ball, but I would like to be competitive and fighting for something important. But honestly, I don't know [if McLaren will win this year]."

Alonso completed 119 laps on his first day at the wheel, which is two more than he managed throughout all of pre-season testing last year. Honda has clearly improved reliability this year and asked if performance has also improved, Alonso said: "Definitely yes. But this is an answer that I had no doubts about. We could not have any doubts because the starting point, all the power and the deficit we had last year compared to the top teams was just too high, so we did improve all the areas of the car.

"From the aerodynamics side there are parts that are quite innovative and new -- in our car at least, maybe the others had these ideas in the past -- but for us they are new and we need a little bit of time to mature the package, and the power unit is the same thing. For us last year was a lot of learning, but we learned many things and now with a completely new philosophy of power unit we still need a little bit of time to understand it and explore the potential."