KUALA LUMPUR, Malaysia — Brawn GP's Jenson Button will start Sunday's Malaysian Formula One Grand Prix from the pole position, with concerns about how his car will perform in the expected rain.

The British driver followed up his pole in Australia last weekend with another strong performance around the Sepang circuit Saturday, setting a best time of 1 minute, 35.181 seconds — more than half a second ahead of last year's pole time.

Button will start ahead of the Toyota pair of Jarno Trulli and Timo Glock, with Williams' Nico Rosberg in fourth. That grid again illustrated the advantage of the three teams whose contentious diffuser designs will be ruled on by the sport's authorities later this month.

"We improved the car overnight and it's improved a lot," Button said, noting the balance difficulties the team had in practice. "I feel very comfortable in the car, so that's exciting for tomorrow. I expected the competition to be pretty tough here, but qualifying was okay."

World champion Lewis Hamilton will begin 12th, with his McLaren still struggling for downforce in corners.

Ferrari's Felipe Massa, who earned pole last year, was eliminated in the first session of qualifying and will start from 16th after an embarrassing miscalculation by the Italian team.

They believed Massa had done enough to get through to the second stage of qualifying and — unwilling to use another set of softer tires — chose not to send the Brazilian back out. It backfired when other drivers posted better times, leaving Massa fuming.

The buyout of the old Honda team by new owners delayed Brawn's start to preseason testing, and the cars haven't performed yet in wet conditions. Button could not vouch for his car's potential in the rain, but was confident of the team's capacity to adapt should the tropical rain arrive as expected on race day.

"It's very difficult to know how it will react to the conditions, the slower pace in the corners," Button said. "This car backwards would be almost as good as last year's forwards. We can get it to be as competitive in the wet as in the dry."

Less than an hour after qualifying Saturday, a storm hit the Sepang circuit, not only lashing it with rain but causing darkness. A similar storm could make conditions extremely treacherous.

Red Bull's Sebastian Vettel was third in qualifying, but received a 10-place grid penalty for an accident in the previous race at Melbourne, dropping him to 13th.

"I personally hope for some rain, because it can mix it up quite a lot," Vettel said.

Brawn's Rubens Barrichello was fourth quickest but a five-place penalty for changing a gearbox pushed him back to ninth.