Button admits engine not McLaren's only problem

While the Woking-based team has struggled with power unit-related issues so far, Button says the car would not be running at the front even if the Japanese engine was stronger.

The Briton admits the McLaren is also lacking downforce.

"We still need to improve in many different areas. We are still very low on downforce," said Button.

"The efficiency of the car, and the driveability is very good, but we are still lacking downforce. But we know that. When you have  that base is very good because then you can start adding more downforce.

"I'm hoping we do in the next few races. Obviously if we had more power we'd be more competitive but we'd still not be competitive enough to fight in front.

"So there's areas we need to improve. Every area needs to be improved."

Button, however, remains optimistic that McLaren will take a significant step forward once the European season starts.

He feels the team has more room for improvement than many of its rivals.

"When you feel that you don't have enough downforce you see more issues with the car. When you add downforce it sort of covers those issues," he said.

"So in a way it's good to find the issues that you have and work around them, so when you have the downforce you'd sorted out the issues already, and hopefully we are going to benefit massively from adding downforce.

"It takes time, but I think there's more for us to gain than a lot of other people.

"I think in Barcelona we'll see a good step."