Button says his Bahrain pace has not yet made him a man to watch out for

The Briton, second in the championship behind McLaren team-mate Lewis Hamilton, was sixth quickest in the afternoon session, but nearly 1.5 seconds off the pace.

Button said both pacesetters Mercedes and rivals Red Bull looked very strong, while he feels he has a lot of work to do before he is competitive.

"At the moment I'm not a guy to watch out for but at the moment the Red Bulls and the Mercedes look very quick," said Button. "The Red Bull is surprisingly [quick] but hopefully we will know a bit more tomorrow.

"There is a lot of work needed in our garage to improve what we have. I'm not happy today, we have tried lots of different things and none of them really worked so we will work late tonight and hopefully find something that will work tomorrow."

Button admitted he did not feel comfortable with either of the tyre compounds brought to Bahrain.

"At the moment I can't make either work," he said.

He added: "The times haven't been good all day, on one lap the Mercedes seems very quick and the Red Bull seems very strong here and on the longer runs, forgetting the lap times, I don't feel very happy with the balance of the car and the direction we have gone in. We have already been talking about tomorrow and there are a lot of positive comments and directions that we can go in.

"For me the car is acting very differently to how it was in the first three races, completely the opposite to what we have had in the first three races so it could be the tyres or maybe just the type of the circuit.

"We have changed the balance quite a bit and maybe we have gone too far and we need to change it back to what it normally is. There is a lot of hard work tonight to improve the car and most of the things we have done have not really improved it."