Barcelona - The McLaren-Mercedes team of world champion Lewis Hamilton have a lot of work to do with less than three weeks to go until the start of the 2009 Formula One season, if this week's testing at Barcelona is any indication.

"We aren't yet where we want to be," admitted Mercedes motorsport director Norbert Haug to Deutsche Presse-Agentur dpa.

"We are far too slow at the moment but are going to work hard to get back to the front."

The problems don't appear to lie with the Mercedes engine as Brawn GP and Force India, who also run with engines supplied by the German carmaker, recorded faster times than Hamilton and team-mate Heikki Kovalainen in the first three days of testing at the Circuit de Catalunya.

For example, Kovalainen was more than two and a half seconds down on Nick Heidfeld's fastest time for BMW-Sauber on Monday.

"We don't know what they are testing but it's a fact that they have occupied the last places with different drivers," said Renault's Fernando Alonso.

Once testing ends in Barcelona, McLaren still have a further four days of testing at Jerez to ensure the MP4-24 is perfectly tuned for the season-opening Australian Grand Prix in Melbourne on March 29.

"We have to use this time (until Melbourne) to improve our performance," said Haug.

Under new regulations, F1 teams are no longer allowed to test during the season. Teams now have to look at new set-ups in the Friday free practice sessions ahead of each GP.

Meanwhile, McLaren president Ron Dennis said the testing in Jerez would be crucial.

"When we get to Australia that will be the first measurement of everyone's performance," he told the BBC.

"We expect our car to go faster with every Grand Prix and we expect to maintain our pace to allow us to win the world championship."