Raikkonen is hoping for a major step forward from the new car

The MP4-19B was run for the first time on Tuesday at Silverstone, with Raikkonen finishing the wet day second fastest to Renault's Fernando Alonso.

Raikkonen said: "My first impression is that the car feels good. It seems to feel and behave really well so far."

The car is expected to make its race debut next month, although McLaren will not say at which race that might be.

The car appears to be a step in the right direction, but it is too early to say any more Martin Whitmarsh McLaren F1 boss

The Mp4-19B features a new chassis and fundamentally revised aerodynamics in a bid to improve the lacklustre pace of McLaren's initial 2004 car, the MP4-19.

McLaren chief executive officer Martin Whitmarsh said the team had not decided when it would race.

"We did what we could considering the weather," he said after Tuesday's test.

"Hopefully, the weather will improve so we can go through a planned testing programme.

"The car appears to be a step in the right direction, but it is too early to say any more."

Technical director Adrian Newey said at last month's Monaco Grand Prix: "In terms of lap times the [computer] simulation says the benefits should be significant, but I would rather not go further than that at the moment

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"It's an updated car so virtually all the mechanical parts are the same. We will be splitting our efforts between testing the car and trying to get it to race worthiness as soon as possible.

"It's not a new car, it's an updated car, so virtually all the mechanical parts are the same, but from the bodywork perspective it's heavily updated and that involves some changes to the chassis."

McLaren had another disastrous race at the European Grand Prix at the Nurburgring on Sunday, when the cars of Raikkonen and team-mate David Coulthard both retired with engine failure.

Raikkonen, who finished second to Michael Schumacher last season, has just one point in the drivers' championship while Scot Coulthard is in 11th place with four points.

Coulthard said: "I think the new car will be an improvement. I believe it will be a step forward and give us a chance to be more competitive.

"Unfortunately it's the same engine. There's still a bit of work to be done on the engine."