Button was not happy after finishing 11th in Australia

The Briton, who finished third in the world championship behind the Ferrari drivers in 2004, said finishing 11th in Australia was "disappointing".

"We have a lot of work to get back up to where we need to be," he said.

"There are some issues we need to address before Malaysia, but I am confident we will have these solved and I am looking forward to the race."

Team-mate Takuma Sato said he believed Malaysia's demanding Sepang track would suit the BAR-Honda more than the Albert Park street circuit.

Button rues 'awful' start to year

Technical director Geoff Willis said: "At Melbourne our poor starting position certainly hurt our race. But our outright speed was clearly not good enough.

"We have had a useful test at Jerez this week where we have been able to investigate some of our performance concerns and we are more confident in our performance for Sepang.

Toyota criticise Honda on engines

"We believe that with higher track temperatures we will be more competitive and we will be looking to take advantage of our new engines for the race."