By Andrew Benson BBC Sport Online motorsport editor

Jaguar driver Pedro de la Rosa has said the team's heavily-revised Formula One car is an improvement on its predecessor - but he could not say by how much.

The Spaniard gave the new R3b its second day of testing at Barcelona's Circuit de Catalunya on Friday and declared that it was definitely faster than the uncompetitive R3.

"We've made an improvement. I cannot say how much - but it's definitely a step in the right direction," De la Rosa told BBC Sport Online.

The team have high hopes of the new car, which is expected to race for the first time at the British Grand Prix next weekend.

De la Rosa says the R3b is a step in the right direction

It features fundamentally revised aerodynamics, including a new front wing, barge boards and diffuser - all aimed at giving it more grip.

Jaguar have been languishing towards the back of the grid this year and hope the R3b can prove that they at least know how to make significant progress.

De la Rosa beat by 0.4 seconds a time set by Eddie Irvine on the car's first run on Thursday, but said the team would need more time to understand the car fully.

His time of one minute 19.683 seconds was 2.5secs slower than McLaren test driver, who was quickest on the day.

De la Rosa was joined at the test by Australian Mark Webber, who was on loan for the day from Minardi as part of a programme to help Jaguar decide who to sign for next season.

He was 0.1 seconds slower than De la Rosa and is understood to have impressed the team.

De la Rosa's team-mate Eddie Irvine has said the new car's performance will determine whether he will want to race for the team next season.

However, the Northern Irishman's contract expires this season and the team are considered unlikely to keep him.

Even if he does say, he will have to take a massive pay cut from his �8m salary.

Spaniard Fernando Alonso, who is set to replace Jenson Button at Renault next year, has already impressed in testing for Jaguar.

Button is in the frame for a drive at Jaguar in 2003.

German newspaper reports have claimed that Jaguar boss Niki Lauda could face the sack if the new car does not show a significant improvement.

Most importantly for Jaguar's image, it must take the team ahead of Arrows.

They use the same engine as Jaguar - built by the Ford-owned Cosworth company - but have substantially less funding.