Formula One testing continued here Friday ahead of the 2010 season starter in Bahrain on March 14 as doubts grew over the viability of new team US F1.

The American grid newcomers have almost certainly been ruled out of the first four grand prix of the season, and are likely to miss the entire campaign, according to the BBC.

It is believed US F1's backer, YouTube founder Chad Hurley, is in talks about switching camps to another new team, Campos.

If US F1 do pull out their place could be taken by Stefan GP, a team set up by Serbian businessman Zoran Stefanovich with backing from the country's government.

US F1 have only one signed driver, Argentinian Jose Maria Lopez.

Campos and the third fresh face, Virgin, lagged behind the rest of the grid in testing Friday, prompting Red Bull's Australian driver Mark Webber to attack the situation as "totally mad".

"I've always been a massive believer that you need quality, not quantity (in F1).

"None of us would really agree to have three or four GP2 cars on the grid with us. That's something we don't want.

"What we want to have is like (Belgian Grand Prix) Spa last year. I remember how close the grid was. The cars were really close. It was a good race and this is how we want F1. We don't want more competitors but less qualilty. We need to keep the quality good."

Webber, who finished a career best fourth in the drivers' championship last season, added: "But I'm all for new people. We need to have new people in the sport because people are not going to be around forever.

"But unfortunately, these people cannot run before they can walk. They are facing a huge challenge, a massive challenge, because how can you learn when you don't test.

"It's absolutely clear that some of the teams are not ready to go to a GP. Some teams are not even going to get to Bahrain."

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