By Sarah Holt
BBC Sport at the Circuit de Catalunya
Webber was nearly a second quicker than anyone else on day one
Mark Webber said he believed his Red Bull team were ahead of their rivals after setting the pace on the first day of the final pre-season test.
The Australian set a fastest time of one minute 21.487 seconds at the Circuit de Catalunya, a second faster than anyone else on Thursday.
Webber, who also suffered a delay when his car stopped on the track, said: "We had a pretty good day's testing.
"Every day is crucial but we're in better shape than the other teams."
On a day when it emerged that new team
US F1 will almost certainly fail to make the grid
this year, and that
Indian Karun Chandhok is poised to seal a drive at fellow new team Campos
, Williams driver Nico Hulkenberg impressed with the second fastest time.
Mercedes driver Nico Rosberg was third fastest ahead of Sauber's Pedro de la Rosa and McLaren's Jenson Button.
It is notoriously difficult to judge form based on headline times in pre-season testing as it is impossible to be sure of the amount of fuel the cars had on board.
We are very confident going into Bahrain
Judging by the manner in which Webber set his best time, it is believed that he was doing some low fuel qualifying runs.
Webber said: "This time is one of the best if not the best in the pit-lane in terms of what we've done last year and what we're doing this year.
"So we are very confident going into Bahrain (for the first race on 14 March) that we're working hard and that the team is doing a good job."
Webber said the Red Bull was in "pretty close to Bahrain set-up", adding: "We had some new aerodynamic updates which worked pretty well and some of that stuff will go to the Middle East."
He said: "It was a clean day's testing apart from a precautionary stop on the circuit because of gearbox oil pressure with a pretty high mileage part, so it wasn't a huge surprise that that had to be done.
"We tried to take it into the afternoon but it didn't quite work for us.
"But there were plenty of positives, a lot of data to dig through before we get to Bahrain."
Asked whether he had any worries about the car's reliability after being forced to stop out on the track at least three times in three pre-season tests, Webber said: "You know, you can always make the car more reliable, there is no question about it."
Alonso's Ferrari had to be towed back to the pits after an electronic problem
Ferrari, who are widely regarded to have had the fastest car at the three tests preceding Barcelona, had an early set-back when new recruit Fernando Alonso stopped out on the track in the morning with an electronic problem.
The Spanish double world champion was seventh fastest overall with a time set early in the afternoon session, 2.683 seconds behind Webber.
Rosberg, who hands over to Michael Schumacher on Friday, said: "I'm feeling quite confident and comfortable in the car.
"Aerodynamically the car will change quite significantly for the first race in Bahrain so we're not focusing on the details but on general set-up work and seeing how the car behaves over long runs."
The new Virgin team had to abandon testing after their novice driver Lucas di Grassi crashed at the 150mph Turn Nine, forcing the team to abandon testing for the day.
Di Grassi said on his Twitter page that he did not know why he had crashed.
But technical director Nick Wirth said: "Unfortunately when we were running some experimental control settings on the car, which were adversely affecting its handling, this caught Lucas out on the entry to turn nine resulting in a spin and contact with the barrier.
"We're going to need to spend the time before tomorrow (Friday)replacing some broken suspension and wings. We should be back on track in the morning, when we hope to really start building up our mileage."
The team are also worried that they have failed to do any pit stop practice so far.
Thursday's Barcelona testing times:
1. Mark Webber (Aus) Red Bull-Renault 1:21.487, 109 laps
2. Nico Hulkenberg (Ger) Williams-Cosworth 1:22.407, 82 laps
3. Nico Rosberg (Ger) Mercedes GP 1:22.514, 107 laps
4. Pedro de la Rosa (Spa) BMW Sauber 1:23.144, 73 laps
5. Jenson Button (GB) McLaren-Mercedes 1:23.452, 101 laps
6. Vitantonio Liuzzi (Ita) Force India-Mercedes 1:24.064, 65 Laps
7. Fernando Alonso (Spa) Ferrari 1:24.170, 74 Laps
8. Vitaly Petrov (Rus) Renault 1:24.173, 74 Laps
9. Jaime Alguersuari (Spa) Toro Rosso-Ferrari 1:24.869, 111 Laps
10. Lucas di Grassi (Brz) Virgin-Cosworth 1:27.057, 31 Laps
11. Fairuz Fauzy (Mal) Lotus-Cosworth 1:28.002, 76 Laps