Button's Honda car is dropping further and further from the pace

Button, who was 11th in Monaco on Sunday, does not even expect to be able to match the fourth place achieved there by team-mate Rubens Barrichello.

Button said: "The car isn't quick enough to challenge the top teams.

"We don't expect to be fourth place from here on out because we know we have a lot of work to do on the car if we are to do that."

Honda are to work on improvements to their car at a test this week, but added: "I don't think all our problems will be solved. We are not going to be challenging the Renaults, the McLarens or the Ferraris."

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Button was dismayed by his car's lack of pace in Monaco.

Having qualified only 13th, he finished 11th after failing to make any impact on the tight street circuit.

"It was hard for me to do anything with the car. I had to stop a lot earlier than I wanted because the tyres were worn out," he said.

"I took lots of front wing off at the stop and the car was much better but this was a race to forget for me."

After the adjustments, Button was left lapping at around the same time as David Coulthard, who finished third for Red Bull after a series of retirements.

But the damage had already been done and he never looked like breaking into the top 10.

"It was good for the team that Rubens was able to do well," added Button.

"I think he was struggling with the same problems I had with tyres but he was helped by a better qualifying performance.

"We're obviously going to have to look into what happened this weekend."