Webber leads Alonso's Ferrari, which he expects to be "there or thereabouts"
Red Bull driver Mark Webber said his team are optimistic of a strong season after the first test of their new car.
The Australian drove the new RB6 on the first two days of this week's Jerez test before handing over to team-mate Sebastian Vettel on Friday.
Webber, who won two races in 2009, said: "The test was very positive. The car's handling well. It has a lot of good traits last year's car had.
"We're in the hunt. Not a second up the road and not a second off the pace."
Red Bull finished last season with the fastest car on the grid, with Webber and Vettel winning the final three races.
Vettel finished second in the championship to Brawn's Jenson Button, now at McLaren, with Webber fourth.
At moment, the top four teams aren't doing same lap times - I don't know what to read into that
Their pace has led many of their rivals to integrate features from Red Bull's 2009 car in their 2010 designs - and meant that Red Bull's new RB6 was the focus of enormous attention when it was unveiled on Wednesday.
Webber said: "We had a great base last year. The rules have changed a lot in a couple of big areas [with the banning of refuelling and narrower front tyres] but the rest of the concept is pretty similar and we naturally have a bit of form.
"When you have form people have expectations, and that's what we'll try and do. We're not right at the top yet - want to go one better. It won't be easy, but we're up for the challenge."
He said he had spent his two days in the car on Wednesday and Thursday trying to rack up as many miles as possible, without trying to optimise the set up of the car for maximum performance.
And he said that it was "pretty close to impossible" to judge the pace of the cars from testing because of the uncertainty over what fuel loads they are carrying.
"At the moment, the top four teams aren't doing same lap times," he said. "I don't know what to read into that. We don't know what the opposition are doing."
He did say, though, that he expected Ferrari and McLaren, who had relatively poor seasons in 2009, to be much stronger this year.
"They're not going to be tugging, are they?" he said. "They're going to be decent. They will be there or thereabouts."
Vettel's first day in the Red Bull on Friday coincided with Lewis Hamilton taking over the McLaren from Jenson Button and Felipe Massa replacing Fernando Alonso in the Ferrari.
But all were frustrated by poor weather at Jerez - there was a brief period of dry running in the morning before rain set in for the rest of the day.
A Toro Rosso driver set the fastest time for the second time in three days, with Jaime Alguersuari posting the fastest lap of the test so far on one minute 19.919 seconds.
Fellow Spaniard Pedro de la Rosa's Sauber was next quickest on 1:20.736, followed by Adrian Sutil in the Force India and Massa's Ferrari.
But the fastest times could bear no relation to actual pace as the teams do not release information about the fuel loads in their cars - and that can make a difference of as much as five seconds a lap.
The new Virgin team finally managed to do eight laps after a torrid first two days with their debut F1 car.
After completing just six laps in the wet on Wednesday, Timo Glock was forced to abandon his work on Thursday following a front wing failure.
The team flew in a strengthened wing mounting for Friday, and the German's rookie team-mate Lucas di Grassi finally took to the track in the middle of the afternoon, when the rain was worsening.